20 Things which will change the world by 2040

Here are 20 things in no particular order which I think will totally change the world over the next 20 years.

1.  CHEAP ELECTRICITY

 Wind costs are falling by 5-10% per annum, solar by 10% to 20% and batteries by 15% plus.  Wind's cost declines will prolly slow over the next 10 years—it's a mature technology.  But the cost declines in solar are likely to continue, and in batteries, there's a real chance they'll accelerate.  If these trends continue (and why won't they?), in 10 years electricity will cost 25% of what it does now.  If the trend decline then halves to, say 7% a year, then in 20 years, electricity will cost just 10% of what it does now.  Cheap energy supercharges economic growth.  The low oil price from 1945 to 1973 helped drive rapid and sustained growth in the world economy.  Cheap renewables will do the same over the next 20 years and beyond.

2.  EVS

They're going to be cheaper than ICEVs (internal combustion vehicles) to buy, and much cheaper to run.  They'll be replacing ICEVs  so the shifts in society might not seem dramatic.  But with AIs running them, transport as a service will become common.  You'll summon a car using your phone, and it will drive itself to where you are and then to where you want to go.  Because EVs will last much longer than ICEVs and will be significantly cheaper to run, "transport as a service" will be a popular way for people to get around.  Car sales are likely to decline by 50% plus, as TAAS takes off.  Air pollution in cities will end.  By 2040, most of the world's vehicle fleet will be electric.  Maybe hydrogen fuel-cell, but I doubt it.  The cost of building a hydrogen refuelling network will be much more costly than just attaching your car to an already existing network, the electric grid.  And the energy efficiency of the hydrogen cycle is much lower than batteries.

3.  AI

I don't think we'll have true AI, as in sentient robots.  But we will have very sophisticated computerised control systems, such as those which will allow for self-driving cars and self-landing rockets.  This has been made possible by the 5 or 6 orders of magnitude decline in the costs of and size of super computers, as Tony Seba points out.  SpaceX's ability to land and re-use its rockets would not have been possible without the advances in computing power.  These advances and changes all interact.

4.  3-D PRINTING

This cuts the cost of manufacturing metal things by at least half, because there's much less scrap.  It also reduces the stock of parts you have to keep on hand.  And allows you to make more complicated things, like SpaceX's extraordinary new Raptor rocket engines.  On the ISS, there is a 3-D printer to make spare parts.  On Mars, and the Moon, 3-D printers will be used to build habitats; to make things which would take too long or are too expensive to get from Earth; and to make things which have short production runs or are experimental.

5.  VAT MEAT, MILK AND FISH

Cheap energy will change agriculture.  Right now, 20% of Australia's tomatoes come from a factory in the semi-desert in the north of the State of South Australia, using desalinated sea water and growing the tomatoes in greenhouses.  This undertaking uses no fossil fuel at all.  Animal rearing  uses vast areas of land, is highly polluting, and contributes 20% to global CO₂ emissions.  Vat meats and fish are already starting to take off.  Their costs are declining year by year.  By 2040, they will become the norm.  

There won't be "real" meat on Mars or on the Moon or in Space Stations .  There just aren't the resources to grow it.  If vat meat, fish and milk taste like the real thing, cost about the same or less, are environmentally kinder, and involve no animal suffering, why wouldn't you switch?  This will reduce emissions by 20% while allowing the rewilding of unused fields and grasslands.

6.  CHEAP ACCESS TO SPACE

Cheap access to space will change everything.  To settle Mars, we'll need to rapidly improve a whole range of technologies, like vat meat production, genuine air conditioning (meaning far more than just heating and cooling), hydroponics, water purification, extracting CO₂ from the atmosphere, genetic modification, medicine, and so on.

By the time SpaceX's Starship is running, SpaceX will have cut the cost of launching a kilogram to LEO (Low Earth Orbit) from $22,000 to ~$20.  Whenever you have a 10-fold decrease in costs you get disruption, as new technolgies take off.   This will be a 1000-fold decrease in cost.  We're already seeing the consequences of cheaper launches in the roll-out of SpaceX's Starlink super fast internet.  The development of a space-faring civilisation will spawn new technologies we haven't even thought of.  Who would have thought 20 years ago that we would carry computers in our pockets millions of times more powerful than the first IBM computer, computers which connect us to a massive knowledge network as well as news, videos, maps, Wikipedia?   None of that was predicted.  Yet think of the businesses which have developed because of those twin inventions, the smart phone and the internet (Apple, Google, Uber, Air BnB ....).  And think also how the explosive growth of smart phone sales also drove down li-ion battery prices,  allowing EVs and grid energy storage to happen.

7.  ASTEROID MINING

With cheap access to space also comes asteroid mining.  Because the asteroids aren't in deep gravity wells like the Earth or Mars, nudging them into orbits which intersect Earth's or Mars's will be cheap.  The resources of a single medium-sized  asteroid, for example for rare earth metals, will more than equal all the rare earth metals that have ever been mined on Earth.   We will prolly stop stripping the Earth to produce metals and minerals and instead start disassembling asteroids to do that.  The world's major resource companies will be asteroid miners.

But some of these will be used in space manufacturing.  Why take stuff into the gravity well when you can build it in LEO?  Asteroid mining will be even more important on Mars, as asteroids will likely provide the volatiles needed to give Mars an atmosphere dense enough for humans to work in without needing to wear pressurised space suits. 

8. BECOME A MULTI-PLANETARY SPECIES

Our first colony will be Mars.  Read  the Red Mars trilogy to see how colonising Mars will change Earth too.  Not just in technological advances but also in social advances.  Looking down on Mars and Earth from space will change mankind's perception of itself.  As Robert Zubrin says, knowing that there is no shortage of resources because we have unlimited resources in space means that most of the causes of war on Earth will disappear.  Of course, no matter how technologically advanced and prosperous humans become, there is no reason to suppose we will ever be more intelligent, less venal, less greedy, and less petty. 

After we colonise Mars, we'll start on Venus.  That'll be much harder.  But by then we will also have colonies in the asteroid belt and large inhabited space stations in orbit round the Earth and Mars.  We will truly be a multi-planetary species.  And that will change everything.

9. TRULY GLOBAL HIGH-SPEED INTERNET

SpaceX's Starlink has kicked off a revolution in high-speed internet.  Starlink's network will be truly global, available in the Arctic and Antarctic,  the Sahara and across the world's oceans.  In countries where wired internet is only available in cities, such as most of Africa, Starlink will provide links to remote villages and towns.  It'll be expensive ($100 per month), but villages could club together to pay for it.  Those same villages are off the electric grid, too, and small solar panels and batteries will change that.  Children who do their homework by candlelight will now be able to do it by LED light, and access the internet, connecting to the ginormous encyclopedia which is the interweb.  20 years ago we didn't have Wikipedia.  Today, even if your village doesn't have a library, even if you  can't afford to buy a book, you'll still be able to study science, maths, languages, technologies.    

10.  TERRAFORMING THE EARTH

The current fall in emissions isn't rapid enough to prevent a rise of more than 1.5 degrees C, maybe even 2 degrees C,  in global temperatures.   We will need to remove CO2 from the atmosphere.  One way would be to cover desert and semi-desert areas with forests.  To do this would require desalination plants, powered by solar, which will get cheaper and cheaper over the next 2 decades.  It would be a mammoth undertaking, almost beyond our imagination.  But it will prolly be necessary.  Given the scale of the problem, any de-carbonisation method will have to be massive.  But something will have to be done to remove CO2 from our atmosphere.  Changing a planet's climate to make it more livable is called terraforming.  You might also call it geo-engineering.  Whatever; we will prolly have started to do it by 2040.  We will have no choice.


11.  GENE THERAPY & GENETIC MODIFICATION

The colonisation of Mars and the growth of space travel will accelerate the development of gene therapy, because radiation on Mars and in space will cause genetic damage.   Treating that will become imperative, and as technology often responds to extreme need, it will likely be developed, because it has to be.  Gene therapy will provides cures for cancer, diabetes, heart disease, and inherited genetic diseases like cystic fibrosis. 

Creating plants which will grow in our domes on Mars and on space stations to provide us with food will be important to the pioneers.   Dwarf wheat, larger tomatoes, low-rise almond/fruit trees, and so on and so on.  The need for these advances will drive rapid change.  But the advances themselves will drive down the cost of food back here on Earth.  


12.  THE RISE OF AFRICA

Africa is the second-largest continent, in population and size, compared to Asia.  For decades, Africa has been an economic laggard.  But solar favours countries near the equator.   Seasonal storage needs are much less than in high latitudes further from the equator.  8 hours of storage will be enough for most places within 30 degrees north and south of the equator.  Cheap electricity will be even cheaper in Africa.  In addition, Africa's population is young, it speaks English as a first or second language, and it's so far behind the production possibility frontier that high speed internet and distributed solar power will be transforming.    

Until recently, Africa has lagged the world economy, but access to electricity and information will change everything.  Africa will be the new China, with high growth rates, falling poverty and  rapid development, and with that will come greater political power.  China has recognised this reality; the rest of the world has not.  That needs to change.


13.  THE END OF NEO-LIBERALISM

Neo-liberalism has been tried for 40 years.  It has resulted in greater economic and financial instability, and vastly increased inequality of income and wealth (especially in those mostly Anglophone countries which have most enthusiastically embraced it), as well as a lower growth rate.   The rising inequality has also led to increased political extremism.  Economists like to pretend that economics is separate from politics.  But the consequences of increased inequality and greater uncertainty have shown that there is a non-economic price for neo-liberalism: the rise of far right parties and policies. The dogma of small government, low taxes, and deregulation is becoming tarnished.  The Covid crisis has conclusively shown that there are some things government does better than the private sector.  Unlike the neo-liberal dogma, the private sector doesn't inevitably do things better and more cheaply than the public sector, especially when second order effects are considered.  Privatisations of state-owned enterprises have mostly failed: costs are higher, services no better, corruption worse.

Expect a gradual retreat from the extreme tenets of neo-liberalism towards a more measured and pragmatic process.  Big(ger) government is back.  The big borrowings government took up under Covid are not going to be repaid.  Instead, governments will start running deficits again.  The post WW2 pragmatic neo-Keynesian synthesis will once again modify red-in-tooth-and-claw capitalism.  

14.  A UNIVERSAL BASIC INCOME

Technological advances will cause major disruptions to job markets.  So will shifts in economic growth and development.  In the past, dire poverty among the old was reduced by the introduction of a universal basic income or social wage for old people, otherwise known as the old age pension.  A UBI in developed countries, for everyone, has so far been seen as a step too far.  But opinion is changing.  If we are truly to drain the poison of the extreme right, we will need to address the insecurity and poverty of the precariat, which will likely be worsened by the technological and economic changes I think will happen.   A UBI would do that.

15.  HYPERSONIC INTERCONTINENTAL FLIGHTS

SpaceX would like to use Starship to run suborbital long-distance flights.  Musk has said that over long distances, suborbital flights will have a lower cost than conventional jet travel.  At 20 times the speed.  Anybody want to bet it won't happen?

16.  NEURALINK

Musk is afraid that a real AI (as opposed to very clever software) would end up ruling the world and humanity would end up being no more than pets of the machines.  If we even survive.  His response to that is to develop brain-machine interfaces.  This would make us as clever as our AI overlords.  We would have chips in our brain, like a permanently embedded smartphone.  It might never get to that, but if an interface can enable a blind person to see again, or a disabled person to walk, then that would be huge.  And having a small device in your head which allows one to communicate directly with the interweb would be revolutionary.  Not sure I like the security implications of that, though.

17.   ELECTRIC PLANES

We will soon see the introduction of electric planes which will allow short flights (up to 400 km) at 1/20th the cost of jet or jet-prop aircraft of today.  They will be used to connect outlying regions to the spaceports where suborbital ultrasonic flights will depart from and arrive at.  The long-term outlook for conventional airliners isn't good at all.  What these two developments mean together is that one will be able to fly from a small town in the bush to another small town on the other side of the world in a few hours.  A hundred years ago, it took 3 weeks for a ship to sail from Australia to Europe.  Currently, it takes 24 hours to fly that distance.  With suborbital hypersonic rockets, the journey time will be down to just an hour.

18.   NUCLEAR FUSION

Nuclear fusion is the opposite of nuclear fission, where large atoms, e.g., uranium, are split into smaller atoms, releasing massive amount of energy.  Fusion is what happens inside stars like our sun, where the lightest atoms, hydrogen, are blasted together under intense heat and presure to produce heavier atoms.  And therein lies the difficulty--it's very hard to create those conditions outside the fiery heart of a star.   For 70 years, the joke goes, nuclear fusion has always been 30 years away. But maybe that's changed.  Fusion is likely to make much faster progress now that private firms and individuals are bankrolling research than it has under the aegis of giant bureaucracies, so I think we'll prolly have fusion by 2040.  We will need nuclear fusion on Mars, and to mine the asteroids.  And it will be enormously useful on Erarth, too.

19.  A RETURN TO DEMOCRACY

Winston Churchill said that democracy was the worst system, apart from all the others.  People have pointed to the Chinese and Russian dictatorships as exemplars of how to run politico-economic systems.   Yet both countries have declining growth rates.  This is particularly interesting in the case of China, which is far from being a wealthy country, and where you would expect growth to remain higher than it is, given where it is in the typical development pathway.  For all America's faults, and despite the out-and out dementia of the Right and the Republican Party, the technological developments there are breathtaking.  Perhaps people need freedom if they are to innovate.  Just a thought.  

If we drain the pus of divisiveness and far-right toxins from our democracies by reducing inequality, and again giving ordinary people hope that their lives and the lives of their children will be better, I believe that the autocratic political/social/ economic alternatives of China and Russia will be seen as what they are: relative failures.

20.  SYNERGY

All these changes will interact, just as smartphones and internet did, the one driving the development of the other.  And the interactions will spiral out of control unforecastably. changing the world in ways which will surprise and shock us.  And some of the consequences will be adverse.  But it's going to be a most interesting ride.

Will SpaceX go bankrupt?

Starship Mk1 at Boca Chica, next to SpaceX's first rocket, the Falcon 1

Suppose, just suppose, the new stainless steel Starship doesn't work.  Maybe it  breaks up on re-entry, because it's a monocoque construction and needs interior ribs.  Maybe putting ribs in it will make it too heavy.  Maybe the welded joins aren't strong enough to withstand the pressure differential between the fuel tanks and space.  Maybe, it's a ship which is going into production long before it's needed.  (Though, frankly, I think, if it works, it will leads to a massive increase in space launches, because it'll be so cheap.)  Maybe the heat shield tiles peel off like they did on the Space Shuttle.  Maybe switching to stainless steel from carbon fibre composite was a serious mistake and SpaceX will have to start from scratch again.

Now I'm not saying I believe all this.  But just suppose Starship is a failure. What would happen to SpaceX?  Well, Musk is on record as saying that SpaceX is devoting less than 5% of its resources to Starship/Super Heavy.  Its Falcon 9 launches are profitable.  Thanks to re-usability, it could cut its charges and still make a profit.  It would survive.  It would be a bitter disappointment to SpaceX and to Musk and to all us Mars tragics, but SpaceX isn't betting the company on Starship.  In fact, because stainless steel is so much cheaper than carbon fibre, to the extent that perhaps Starship could be built for under $10 million, it was a bigger bet before. 

So that's the downside: less than the cost of a single Falcon 9 ($60 million) wasted if Starship fails.

The upside is that Starship works. 

In the pictures from Boca Chica, Starship looks like something out of a SF story.  But the first planes built weren't the smooth, shiny monsters they are today.  You could see where the aluminium had been beaten and nailed into shape.  You could see the rivets.  Yet aircraft went from things covered with painted canvas to the Airbus A380 or the Boeing 787, from contraptions that were dangerous and expensive to safe and cheap.  The chances are that Starship will work.  My doubts about the monocoque construction are the doubts of a non-engineer.  Musk and his team of engineers know what they're doing.  The proof of that is Falcon 9, Falcon Heavy, Dragon and (shortly) Crew Dragon.

The other risk is that there is no market, that this mammoth machine is just too grand for the limited demand for launches.  But the demand for launches is limited by cost.  If the cost of lifting a tonne to LEO (low Earth orbit) falls one hundred fold, as it will if Starship is successful, the demand will explode.  If nothing else, Starship will be able to take people up into orbit for a week's "spacecation", and do it profitably.  A bit of a come down from starting a Mars colony, but nevertheless, survival.

And if Starship is safe, and works, and is re-usable, it will be irresistibly cheap to NASA and ESA and anybody who wants to get to Mars and the Moon.  NASA/ESA/Roscosmos will simply buy berths and cargo space on Starship to start their own national bases on the Moon and Mars.  The first bases will be scientific, but they will develop into refuelling stations, to fuel the ships that will travel to mine the asteroids.  There will be space stations orbiting around Mars, and ships heading out to or back from the asteroid belt will refuel there.  There will be space stations orbiting the Earth, and space manufacturing will start. 

The upside is huge.  Right now, Musk says that SpaceX will just build the ships to get us to Mars and the Moon.  After that, it's up to everyone else to get things working.  But SpaceX will have improved or developed technologies such as life support systems, food growing, extracting CO2 from the air (which will work just as well here as on Mars, and which is desperately needed on Earth), spacesuits, Martian/Lunar powerplants.  These will be sellable.  And the logic of gravity wells suggests that the Mars-Earth spaceships will be built in orbit, docked at a space station, then will travel from Mars to Earth and back without ever entering an atmosphere.  The Starship shuttle will lift passengers and cargo and fuel from Earth or Mars to the space stations, and then the SpaceX spaceliner will carry passengers in luxury from the space stations orbiting round one world to space stations orbiting the other.  In all these endeavours, SpaceX will be the market leader.  It will have learnt how to build in space, to work in space, to travel across space, and that will be hugely profitable.

So there it is.  SpaceX isn't betting the shop, as Tesla did with the Model 3.  For just 5% of its resources, it is building the base for a massive expansion of space-related business over the next 20 years.  That seems like excellent odds.  SpaceX won't go bankrupt, it'll thrive.

Getting to Mars--cheaply

Asteroid mining. Source

NASA estimates a cost of $100 billion for 5 astronauts to get to Mars and back. $20 billion per person!  It's no wonder the date mankind will reach Mars is always 15 years from today.  No government will fund that kind of expense.  But what if the cost could be dramatically, massively, cut?

If SpaceX manages to make the BFR and BFS reusable, even for just 10 times, the cost of getting to Mars will be 4 or 5 orders of magnitude less than NASA's mission.  (An order of magnitude is a 10 fold increase or decrease)

There are three parts to the Falcon 9: the first stage, or booster; the second stage; and the payload which is protected by a fairing.  Already the Falcon 9 first stage is being used twice, and with each successful launch and relaunch, the steps needed to reuse the first stage have been reduced and the speed with which SpaceX can reuse them rises. But the second stage and the fairings are discarded, and allowed to fall back to earth where they burn up in the atmosphere or crash into the sea.

We know from SpaceX that each launch of the Falcon 9 costs $62 million, and the launch of Falcon Heavy costs $90 million.  Musk has said that the fairings cost several million, but he has also said that the first stage is somewhat less than 75% of the total cost.   Reconciling these two statements is beyond my skills.  So let's assume that the second stage plus fairing costs 1/2 the first stage.  That gives us 3 equations, where A = the cost of stage 1, B=the cost of stage 2 plus fairing and C = profit margin.

(1) A+B+C=62
(2) 3A+B+C=90
(3) B=A/2

Three variables, three equations--hey, I can solve that!  And the solution is:

A (cost of stage 1)=$14 million
B (stage 2 + fairing)=$7 million
C (profit) = $41 million

The high profit margin (66%) explains why SpaceX is still going despite its heavy outlay on development, and despite frequent predictions that it was in imminent danger of bankruptcy.  (In that sense it's not really a profit margin, rather development cost recovery)

Undoubtedly I've got things wrong, but it gives us some reasonable guesses.

Let's use the number of engines as a proxy for the cost of the BFR vs the Falcon 9.  I know that's far from exact, but the engines are a big part of the cost and if they are all the same size, the number should be proportional to the size of the rocket, and therefore its cost.  The BFR (i.e., stage one of the Mars Transporter) will have 31 Raptor engines, compared with the Falcon 9's 9 Merlin engines, so a very rough calculation would put the cost of a BFR at 14/9*31=$48 million.

The BFS (the upper stage of the BFR, the proper "spaceship") will have 4 vacuum Raptor engines and three smaller atmospheric "sea-level" engines) The BFS will cost much more than stage 2 and fairing of the Falcon 9--it'll be much bigger and will have life support (though the tanker and cargo versions won't.)  To get some idea, let's again assume the rule of thumb we used with the BFR.  That suggests the BFS might cost 14/9*7=$11 million.

Now, profit/development costs.  Much of the development cost has already been spent, with the development of the Raptor engine and the composite-fibre fuel/lox tanks.  But this still has to be redeemed from future launches.  Let's assume that the profit/development costs are 5 times the profit on the F9, or roughly $200 million.  That gives a total cost of about $260 million. That's for ONE use: if the BFR/BFS combo can be reused just 10 times, the cost per launch drops to $26 million.

Musk thinks the BFR can be reused 1000 times, the BFS 20 times.   But BFS reuse assumption is low because it's being used for Mars journeys, which means 2 years between journeys because Mars is only in opposition to Earth every 26 months.  If it's used for journeys to the International Space Station, the moon, and to launch SpaceX's fleet of satellites for its world-wide internet system, its reuse will be greater.  On the other hand, maybe it's just impossible to actually reuse spacecraft several times because the rigours of launch and re-entry are too great.  I've seen estimates of 12 reuses of stage 1, followed by a major refurbishment.  Refurbishment will however be expensive.  So let's ride with 10 reuses.  Even that will be enough to make the BFR/BFS combo ridiculously cheap.  And 12 reuses will cut the cost another 20 percent, 20 reuses by  50% more.

The cost of fuel is (relatively speaking) negligible in this context: $200K for a F9, so perhaps $1 million for the BFR. So the cost of each launch (with 10 reuses) would be $27 million. For a Mars trip, the BFS will have to be refuelled in space 7 times.  That suggests the total cost of the first Mars trip of $432 million -- $216 million each for one manned ship and one cargo ship, with 7 refuelling flights for both. Subsequent launches will require less cargo, because machinery will be manufactured on Mars using 3-D printing and local resources, so costs will fall sharply.  Each manned ship will be able to carry 100 passengers, so cost per passenger will be under $500K for the first few trips, much less thereafter. (This compares with $5 billion per person with NASA's current plans.)  However, Musk reckons the total cost per launch will be lower than the Falcon 1, which was $7.3 million in 2015 dollars. This is way lower than my estimates, which means he is assuming more reuses than I am--at least 30 or so.  However for the point to point rocket flights on Earth, to get the cost down to the price of a business class air ticket, you'd need to get 100 reuses.  Hmmm.

The key is reusability. If SpaceX delivers that, especially if they get even 100 reuses, the whole solar system opens up to manned exploration. People have consistently dismissed Musk's plans, with both Tesla and SpaceX. And he's achieved all his goals, though admittedly it's usually taken longer than he said ("Elon time"). Perhaps most significantly, where NASA, ULA, Ariane, Uncle Tom Cobley and all seriously doubted or even rubbished his efforts to make rockets reusable, he succeeded. The first few landings failed, right enough. But there have been 20 perfect landings in succession to date.

Musk has clearly dismissed any hope of finance from NASA.  SpaceX generates a "profit" of $41 million per launch of the F9.  That's $6.1 billion over the next 5 years with 30 launches a year (SpaceX will have half the market this year), enough for 26 BFR/BFS sets, assuming $200 million "profit" per set.  But of course, SpaceX will be selling the services of BFR when it is built, getting revenue that way.  When the BFR/BFS becomes the workhorse rocket within the firm, launching satellites and servicing the ISS, SpaceX will be making $20 million per launch.  And given the probable elasticity of demand for space services at much lower prices (remember the BFR/BFS will carry 150 tonnes to LEO compared to F9's 22.8 tonnes,  at a cost of $180K per tonne vs $2.7 million per tonne), there will likely be thousands of launches per year, not 60.   Development costs will be spread across far more launches.  Up until SpaceX slashed the cost of space launches, it cost $22,000 per kilogram, or $22 million per tonne to get stuff into orbit.

Why does all this matter?  

Well, there is already one spin-off.  Cheap satellite launches will make SpaceX's world-wide high-speed internet feasible.  In the past, the biggest component of satellite costs has been the launch.  A truly world-wide high speed internet, available in the middle of the Pacific, the Amazon jungle, the Sahara desert, Africa, outback Australia, etc, not just in wealthy cities in the West, will transform the world.   SpaceX envisages that you will need no more than a book-sized receiver on your roof to access internet speeds 180 times faster than they are on average in the world today. 

Another possible spin-off: to extract CO2 from the Martian atmosphere, SpaceX will need to develop its own machinery or use machines created by others. Just as they have with everything else, they'll cut costs and improve efficiency.  What works on Mars will likely work on Earth too.  This will be tremendously useful on Earth.

Probably, all the things we'll need to do to maintain life in our domes on Mars, and later on its surface, will have useful applications for Earth too.  NASA is responsible for a long list of useful inventions which are spin-offs of the space program.  Solar panels were first developed for use in satellites.  Now they will save the world by replacing fossil fuels.

The asteroid belt beyond Mars and near-Earth asteroids closer to Earth are a treasure trove of minerals, containing a planet's worth broken up into bite-sized chunks.  The BFR will make getting to the asteroid belt cost effective, and shipping minerals back will be cheap because the asteroids have hardly any gravity--a small push will send them on their way to Earth or Mars.  Mars will be a way station for miners in the asteroid belt, because it's much closer than Earth.  So they will likely also mine the asteroids for water and ammonium (for the nitrogen) for Mars, as well as minerals for the Earth.

When the mobile phone and the internet were invented, no one could foresee how they would revolutionise society, or how disruptive they would be to established industries.  Cheap space travel will change the world for ever.  We will start a colony on Mars, we will mine the asteroids, and the spin-offs from rapid technological advancement in space will change our lives here on Earth in ways no one can foresee.   That's if we don't blow ourselves to bits with nuclear war before that.  Or cause global temperatures to rise by more than 1.5 degrees C, which will lead to huge adaptation costs in low-lying cities as well as massive numbers of refugees. Or do something else stupid.  I live in hope.

[Update 21/1/18:  I found a news report where Musk costs the fairings alone at 6 million.  If you recast the equations so that the cost of stage 2 without fairings is 75% of the total cost before profit, the cost breakdown comes to something like this:-

Stage 1--$14 million
Stage 2--$4.6 million
Fairings--$6 million
Profit/Development cost--37.4.

So profit margin 60% not 66%.  The cost of the BFR/BFS doesn't shift much.]