"Hundred dollar hamburger" explained

[The phrase is] used in general aviation in the United States (perhaps with variations on the theme elsewhere?). A lot of pilots like to pick a random airport a couple or a few hours away, drop-in for a meal, refuel, and then take off again to fly back home. The sheer joy of flying seems to serve as the primary motivation, like someone taking a sports car out into the countryside for a weekend getaway. The $100 price tag refers to the cost of flying to a distant runway for no reason other than wanting to fly to it, and not specifically to any meal that may have been purchased there. It’s a euphemism, or a wink-and-a-nod, or both, even though fuel prices today would make a hundred dollar round-trip flight a bargain."

Via Twelve Mile Circle, which has links to relevant sites.