[Lerc]

Cost per tokens is as valid as price per unit volume of fuel.

Changing the fuel type, efficiency of your vehicle, driving distance, or driving conditions will all change how much it will cost you.

Fuel cost per unit volume does not become meaningless just because you are neglecting all of the other factors involved. That would be throwing away the only data point you have been using.

This is just asking for someone to amalgamate all of the factors involved into one simple, easy to game, index.

[Aurornis]

That’s not a good analogy because a gallon of gasoline has a known amount of energy in it. The efficiency of each vehicle is also known, at least in a way that is easy to compare on a relative basis.

I can go to 10 different gas stations and buy the same amount of energy from them. When I put it in my car I’m going to get the same result out. The differences are very small.

[bjt]

Except, a gallon is a gallon no matter which gas station I'm at. Also I know my car's gas mileage, and it doesn't change when I visit a Shell station instead of a Chevron. The composition of the gas is regulated, as are the pumps that dispense it. There are inspectors from the state whose job it is to ensure that when I buy a gallon, I really get a gallon.

Tokenizers aren't standardized to anywhere near that level. A "token" from one isn't the same as a token from another.