Eating enough protein and calories to recover during weightlifting programs can be a difficult proposition if your budget is tight. The following five foods are high protein foods that are relatively cheap. (Values based on Sam's Club prices)
With 56g protein/$, milk is the victor as highest protein per dollar. It's easy to consume, readily digestible for the majority of humans, and is delicious. In addition, there are many types of milk with varying fat quantities, so if you're trying to gain weight or lose weight, milk has your back.
Close to milk, chicken has 51g protein/$. Chicken is the bodybuilder and weight loss lifter's best friend. It's almost entirely protein with very little fat. It can also be prepared in a variety of ways: grill it, barbeque it, marinate it, bread it, bake it, stir fry it, sear it, and do pretty much anything you can think of to it.
If chicken is the weight loss source, peanut butter is the antithesis; peanut butter has 39g protein/$ and 15% of it is protein, which means it's a massive 1,100 Cal/$. Burger king can't even compete with that.
Whey powder (NOW Foods 100% Protein Isolate) has 33g protein/$ and can be bought in a variety of flavors. It's great if you're low on time or aren't a big eater in the morning. Many trainees love to use whey powder as a post workout ritual.
90/10 Ground Beef
Probably the most versatile of the list, 90/10 ground beef has 31g protein/$. Like chicken, it can be prepared in many ways and is awesome if you're bored of eating chicken at every lunch because you've been trying to lose weight for three months.
Notice that all of these foods are basically single ingredient foods. This is generally the case for high quality, cheap meals. Highly processed foods will cost more and contain much less protein per dollar. Protein is essential in recovery, but that doesn't mean you need to buy the best whey powder that Olympians endorse. Chicken, milk, beef, peanut butter, and cheap whey powder will serve you just fine and won't drain your wallet.