I made this quick tortilla soup that I really like and it is cheap! if you grow your own tomatoes and cilantro, it can be pennies!
In the blender grind 2-3 c. stewed tomatoes or canned whole tomatoes, 1/2 onion, 2 cloves garlic and blend until smooth. Pour into sauce pan and add 2 c. chicken broth, 1 t. cumin, 1 T. california chili powder, 3-4 springs of cilantro and simmer for 15 minutes.
You can serve this with all sorts of add-ins and toppings or eat with just some cheese on top. Some of the toppings I like is whole kernel corn, cheese and torn corn tortillas. You can also put avacado, sour cream, diced cooked chicken, rice, chips or whatever! It is really good and filling!