|steak and eggs at Billy Goat O'Hare|
It serves basically diner food, burgers, sandwiches and eggs. While the prices are still higher than what they charge in town, you can get a plate of eggs, hash, toast, and some sort of dead animal flesh for less than ten bucks. This is not good food either, but not the worst, especially when you are stuck there for a 2.5 hour layover.
(probably the best food at O'Hare though is the more recent addition, Torta Frontera, of the famed Chicago chef Rick Bayless. Really fresh, well prepared food at seemly reasonable prices.)