1. One of my favorites is the Hard Rock Cafe's baked potato soup. The recipe is online, just type the title into google.
But the instructions tell you to bake the potatoes, then peel and dice them. I don't. I found another use for them.
Instead of just peeling them and dicing them, carefully slice them in half the long way. Scoop out the potato and proceed with the recipe. Then slice the two long halves into two more, so basically you have 4 long potato "boats". If they're really large potatoes, you could make 8 skinnier "boats".
Now use those to make potato skins the next day, or a day or two later. Just keep them covered and refrigerated until you're ready to use them.
When making the potato skins, heat the oven to about 400 degrees. Lightly spritz the skins with olive oil or lightly brush with your choice of oil. Lay them on a baking sheet and bake the skins until they're lightly golden brown and crispy.
Then top with your favorite potato skin toppings: shredded cheddar, blue cheese, sour cream, crumbled cooked bacon, chives, diced tomatoes, whatever you like on a potato skin - loaded up or just simple! You get two substantial meals out of a few baked potatoes.
2. Another cheap way to begin a vegetable soup: make corn cob stock. Strip the kernels off of several ears of corn (a great way to use those end of the season ears of corn that might not be so pretty as the ones you bought this summer). Get a large stock pot, fill it with cold water. Break the cobs in half and immerse them in the cold water (make sure they're covered). You can use plenty of cobs, and a big old pot of water. I use a 12 quart pot and about 8 large cobs. Of course, you can make a much smaller pot and use fewer cobs.
Boil them for about an hour. Then remove the cobs and compost them or discard them. Keep simmering the water until it's reduced by about half.
Then saute or roast chopped vegetables. Use the corn kernels, diced onion, sliced zucchini or summer squash, diced winter squash, sliced carrots, shelled edamame, cooked lima beans - whatever is available and affordable that you like; a little for a thin soup, a lot for a thick stew. Add to the corn cob stock, and if you like, add pasta and cook until it's al dente. You could also add small cooked meatballs, or cooked chopped chicken for a heartier meal. It's a really cheap way to make a healthy vegetable stew out of cheap fall vegetables, with no preservatives, artificial stuff or additives.