You can buy bags of dried beans at the grocery store for around a dollar each. The bagged beans actually taste better than the canned beans, and they are much cheaper. Just remember, some beans need to be soaked overnight before being cooked!
For example, you can make a giant pot of lentil soup that will have 10 servings for maybe $4 worth of ingredients. And it's healthy.
Split pea soup is another good one.