Here's one we love that's really cheap if you use some substitutions. I usually double it.
Hearty Black Bean Soup
2 cans black beans (or 3 C cooked beans)
2 C chicken broth (I use homemade stock)
1 C salsa (again, homemade fresh)
2 tbsp. chopped cilantro
2 tsp. lime juice
Cook salsa over med heat for 5 minutes. Add beans and broth, simmer for 15 minutes. Remove half, let cool, then puree in blender. Return to soup pot, then stior in cilantro and lime juice. Heat and serve. yummy!