I have a family of 5.
And I can feed them for around $10.
It's quite simple: go to many of the fast food places (McDonald's, Burger King, Wendy's, etc.) and you'll find a dollar menu.
We just cut out the drinks, because they seem to pack it full of ice anyway.
Each family member gets a sandwich and fries.
I know, I know, it's not the healthiest but it'll do in a quick pinch.