Lentils are another great legume that can be found for cheap, and are a lot easier and quicker to prepare than most beans.

Oats are another really healthy alternative, and have a lot of health benefits not found in wheat and rice. I like adding oats to ground meats to really stretch out things like meatloaf, meatballs, and such.

Some warnings, changing your food intake to include a steady diet of legumes can cause some gastric distress and flatulence problems. It is advisable to make such transitions slowly, and augment your diet with things like yogurt (Activia is good) and other cultured foods. Also, be aware that any radical increase in the consumption of carbohydrates can place some stress on your insulin supply system. I know of a couple people that tried to make the conversion and they ended up with diabetes shortly after starting. Also, some people become sensitive to glutinous food consumption (celiac disease?).

Economics may not give us much choice sometimes in being particular about what we can stock. We've come a long way in a very short 10,000 years, and being essentially omnivores has given us a lot of options about what we can put in our gullet. I can well envision a time in our near future where we might be eating something like a paste, or a moist loaf, or maybe little green wafers??? Nutritionally sound, but leaving a lot to be desired on the pallette. But if it is a choice of eating the same thing all the time or not eating, I will take what I can get I am sure.

Don't overlook noodles. They can often be found for cheap, are easy to store, easy to cook, easy to digest and versatile.