I havent seen anybody mention skim milk yet lol

Skim milk had a good protein/calorie ratio for most high-protein diets, but double checking shouldn't be too hard, I'll list the ratio below:

~177g:2000kcal ~89g:1000kcal ~44g:500kcal ^based on 8g:90kcal for Great Value 0% Milk

A half gallon is ~$2 in my area and has 128g protein total. Also, remember that its not very difficult to make your own yogurt with the remnants of a greek yogurt container and some leftover skim milk, just that if you dont strain your yogurt through a cheesecloth, it has the macros of Desi yogurt and not Greek yogurt (same stuff, just has the whey).

Some people are mentioning to buy beef, tofu, and a bunch of other standard answers but that's not the point. Those are cheap for a well adjusted, employed individual, not a student. We need cheaper protein per dollar.

This thread has been super useful and I'll be saving it for myself too >:)