I am surprised no one has mentioned Taim, in the WV. Awesome falafels.
That, and Caracas Arepa Bar in EV - Its not exactly great value for money at $7 for an arepa, but the food itself is pretty decent.
What about that burger joint at Le Parker Meridien?
Funny thing is, moving out of NYC and living in Mumbai now, cheap food has taken on a whole new definition. $14 for a f'in pizza?! Gotta be crazy