What is the science behind an overpriced airport beer hitting the spot more than drinking it anywhere else?

WTF. My girlfriend and I were talking about the same thing exactly around the time you posted this! We were in JFK, heading home from a holiday in New York. We had about $26 cash left so went to grab a beer each while waiting for the plane. Knowing the prices we had paid in the city we ordered one small and one large beer, thinking $26 should cover it with change for tip. The bartender poured one large beer, then started pouring another, even larger beer. I asked what was going on and he said this is one small and one large. Apparently at this bar the "small" beer was not half a pint (or less as other bars in the city), it was 440ml, which is the size of a tall can. The large beer was 660ml, more than a pint. The total came to $37, I gave him the last of my cash and asked to pay the rest on card telling him he wasn't getting a tip. We sat down, pretty fuming from being ripped off, but goddamn those were 2 of the best beers we'd had in ages.