Beans are one of the cheapest sources of protein around, especially if you buy dried and cook them up in a pressure cooker. They are also versatile, and (I think) delicious.
Vegan Dad's recipe, but changed it around to incorporate okara. We had some leftover from dinner, so he made a big salad with spinach, tomato, grated carrot, cucumber and more chickpeas. This was a delicious and huge Sunday lunch.