I could give a long description about the process to make the sugar needed to make cola, and then describe whiskey as essentially just water and alcohol, and some flavors. Then there is that other kind of alcohol, methanol, for cleaning windows etc, usually sold in percentages over 80%. How much does that cost per liter? I stand my ground that spirits could be sold for about the same price as soda, if it would not be taxed with special exise, duty, tax, or whatever the special "alcohol tax" is called in your country. Which is exactly the reason that in practically every country alcoholic drinks are made artificially more expensive.

All you say might be true for the current design of airplanes. But it is like saying, "this formula 1 race car is really more efficient on the race track than in urban traffic, hence driving cars faster is more efficient.". I agree flying higher is more efficient. There is however no rule that you need to get to 400kts in order to be able to fly at FL350. It all depends on the design of the airplane. In general, for every form of transportation, road vehicles, boats, airplanes, going faster always means "spending progressively more fuel". I built my own airplane. And sure enough, flying it at 160kts instead of 140kts costs more fuel, at any altitude. And, not insignificantly, my small propeller airplane has a lower fuel consumption per passenger per mile than the airliners do, despite the latter flying higher and faster... What is the reason of that? There was also the Concorde. It could fly even faster, and higher, but... it used way more fuel. But this also doesn't mean that flying the Concorde close to its stall speed would be more efficient. There is no way to fly the Concorde at the same efficiency as a 737, at any speed or altitude, because it is designed to fly high and fast, and burn more fuel to make that possible.

So, I'm pretty sure, if we would not optimize the design of airplanes for a certain speed, but for the lowest fuel consumption, you might indeed end up with airplanes that fly slower (and maybe lower) than the designs we have now, and we could have airplanes that use less fuel per passenger per mile.

If it is about hormones, why then also not test for growth hormone (GH)? People with more than average GH might have longer legs, giving them an advantage in certain sports. There is also Adrenaline, Cortisone, etc. also giving certain advantages. Maybe we should try to cancel out ALL natural variations, to make the competitions more fair. In the end, we can only allow exact clones from each other to compete to each other. And end up with competitions which equal to throwing a dice, because nobody can be truly be "the best" anymore, which can be defined as "possessing the best set of natural variations that makes this person a born winner".

I think even in the US there is more tax on your car's fuel than on the airplane fuel. And I'm pretty sure there is some special tax on whiskey and other concentrated spirits, and tobacco, etc. Even in the US tax is used to direct social behavior.

It is not the airliner which is the problem, it is the government. Compare it with the tobaco and alcohol industry: You can't expect them to protect the health of their customers and to reduce their profit voluntarily, If you want to reduce alcohol consumption, you just need to make the stuff more expensive with taxes etc. A bottle of spirit would cost the same as a bottle of cola if the government would not interfere, it is the task of the government to avoid this danger to society. The same with air travel: To make air travel less attractive is not the task of the airliner but a task of the government. At this moment, airliners are pampered, get tax free fuel, can expand at the cost of the neighborhood, etc. so what do you expect?

The air travel industry doesn't care much about fuel consumption. They still descent with flaps and spoilers out, instead of trading off altitude for speed slowly. They fly with speeds of 400+kts, but just like with cars, going slower saves fuel. And as long as the airliners demand fast airplanes, manufacturers keep designing them, despite the higher fuel costs compared to a slower plane. Again, making fuel much more expensive could cause the industry to rethink their strategy. There is a tipping point where customers accept a longer flight time for a substantial reduce in costs.