Except obese people don't have to pay for two seats, as
ruled by a Canadian court. The rest of your post is a series of non sequiturs, because there is choice in the same price range. I can buy shirts that fit me for the same price as a smaller person. The materials might be a bit cheaper, or the cut might not be as great, or it might not have a brand attached to it, but it'll fit me. I can do the same for cars, and for anything that's property. An airline ticket is a service, and there is NO choice. I can't decide to trade that second carry-on weighting 20 pounds that every person brings but that I don't. I can't decide to downgrade the seat's materials, or not to have food included, or to have to pay extra for every inch more that I want. I don't have an alternative.
Also, your money comment is absurd. Tall people
tend, on
average, to make more money than shorter people, but that in no way means that I have a few thousands magically floating in my pockets. I generally have less money instead, because between the clothing, food, doctor visits (for back problems, neck problems, knee problems, you name it) and whatever else, my student money isn't going very far. But don't let that get in the way of a nice juicy overgeneralization.