some things that we do when we don't want lentil soup (which we fortunately like but do get sick of) but still want cheap
- vegetarian tomato sauce (canned crushed tomatoes, fresh seasonal veggies, jarred olives, dried basil and oregano, salt, pepper) with pasta.
- salmon cakes (canned salmon, eggs, breadcrumbs, dill, parsley, lemon, salt) with potatoes.
- pea soup (dried peas, onions, carrots, potatoes) with bread.
- tofu stir fry, try asian store for cheap tofu (tofu, veggies seasonal or frozen, soy sauce, ginger fresh or powdered, onions, garlic) with rice.
- tofu in coconut milk and curry (tofu, can coconut milk, veggies fresh or frozen, thai curry paste (many flavors available cheaply at asian grocery stores, lasts forever)) with rice. this is how i originally got dp to eat tofu at all
also, i know you said that you don't like lentil soup, but i do have one recipe for red lentil soup that even my lentil-disliking dp finds delicious, let me know if you want it.