I like to make chicken and vegetable soup. I take 2 chicken breasts or about a pound of chicken burger (if I use burger I brown it, if I use breasts I slice them thinly). Then add water, chicken or vegetable broth, canned beans (mixed or chickpeas), bring it to a boil, then turn down the heat to a simmer. Let it simmer for 2-3 hours (until the chicken just starts falling apart), then add carrots, potatoes, Bok Choy, eggplant, or whatever kinds of veggies you have/like. Then simmer it for about another hour. 1 batch usually feeds my 3 person family for about 2-3 days.
The bonus is, to a point, the soup gets better as it ages as long as it's refrigerated. After 3 days if you have any left, you can just freeze it in Tupperware. In the winter I cook it on the wood stove, so it takes a little longer, but other than my labor, it doesn't use any electricity or gas for cooking. All in all for 3 days of eating I'd say that it costs around 5-10$ to make, if it's just you eating it will last even longer. You can also add dumplings if you want, substitute the meat for different kinds of meat or just make it a vegetable soup.