Our big fill-you-up-cheap item was pizza. The ingredient cost for pizza is ridiculously low, even for above-average quality ingredients. An entire pizza was likely $0.50 or so, depending on toppings.
The restaurant oven was this giant gas-fired thing with 5 or 6 circular, rotating stone surfaces with each set to its own temperature. The pizza stone was set somewhere between 550 and 600° F.
My main job was making the pizza, and they were good. Definitely better than anything you could get at a Pizza Hut or Dominos or Little Caesars. People would even ask for custom pizzas, and management didn't care. You put it out on the buffet line and wave at them so they know it's ready. Of course, while they're waiting they aren't eating other things...
The restaurant also had a little game room with arcade machines that spit out tickets for cheap prizes. Kids would have a slice or two of pizza and then run off to play games, making their visits especially profitable.