Changi Airport in Singapore definitely has reasonably priced food in most areas, both fast food and restaurant styles. For the real cheap eats in SIN though (if you're landside) then it's worth going down to the employees food court - great authentic food at low low prices.

They're not signposted, but in Terminal 1 you can find it by walking past the Burger King on the arrivals level, then down a flight of stairs around the back and into the basement of the connecting building. Well worth the trek! ^