Guess what happens when asinine security measures prevent travellers from bringing their own bottled water into the terminal? Profiteering on the part of the shops in the terminal.
But Pete, isn't everything at the airport expensive? Well, usually. But the $4 1 liter bottle of water I bought typically costs $.99 at 7-11. 4x price differential. The King Size packet of Skittles I bought at the airport shop was $1.99, maybe 50% more than at 7-11.
The point? Whatever 'convenience margin' airport stores typically charge, this one is clearly exploiting the fact that it has a monopoly on packaged water past the security checkpoint. And that's lame. Thanks TSA. Not only do you make my security experience suck, now you make my refreshments more costly as well.