One of my favorite low cal foods is a tuna salad. Can of tuna $1.50, lettuce maybe 40 cents, half tomato 40 cents, a third cucumber 30 cents, carrots 25 cents, mushrooms 20 cents, light italian dressing is $2.00 and I might use about 10 cents of it, and it comes to about maaaaaaaaaybe 300 cals.  These are all estimates of course, for the exact price of what goes into the salad but it's about $2.00 per salad, filling, and easy to make. You have to spend more initially to get all the ingredients but then you get multiple uses out of it. Stupid fat people.