(Cost) What is the cheapest whole food that gives the most protein?

I've recently been eating a lot of pasta and rice with marinara sauce and ground beef, sometimes I add a few eggs to the sauce to give the sauce a slightly creamy consistency. I also make delicious frittata's and scrambled eggs for breakfast. But I've been trying to add more protein to my diet and I was wondering, what is the cheapest food that gives the most protein? I know that ground beef is delicious and economical, but chicken breast gives more protein and is just as economical. But what if you want to take it a step further and get something even more delicious, nutritious, and cheap? The answer is beans and lentils. When I was a kid I remember eating beans and lentils a lot, they were delicious, filling, nutritious, delicious, and CHEAP. Beans have 15 grams of protein per cup and lentils have 18 grams of protein per cup. So I decided to make a big pot of lentil soup and a big pot of bean stew and freeze it and save it for whenever I wanted a cheap, nutritious, and delicious dinner. So if you're looking for a cheap, nutritious, and delicious dinner, then give these recipes a try. Lentil soup, bean stew, chicken and rice, ground beef and pasta, frittata's, and scrambled eggs.