the reason the water is so expensive after TSA is that the airport is charging an outrageous amount of rent. the rent cannot be covered with prepriced merchandise(magazines & newspapers), so they jack up the price on everything else. i think running a concession in the airport is not profitable unless you have huge margins and a pretty good gross.

the water price is the same as the taxes on a rental car. soak the tourist.

for water, you can collapse the bottle in your carryon. if there are no waterfountains, the restrooms usually have water(not always). that is usually the same water you would get out of the water fountain.