I mean I think chicken is king of quality protein per cost, so nothing can really top that IMO but here's some stuff I eat:
-I really like marinating lean beef in KBBQ sauce, cutting into thin strips, and grilling it, freaking delicious
-Eggs, either in an omlettle with onions/cilantro/green chile or soft-boiled and marinated like a ramen egg (mirin/soy sauce mix)
-Cottage cheese is like roughly ~50% protein by calories, reasonably dense, and fairly cheap
-I know some idiot will get mad over this, but Tofu is like 50% protein and absolutely dirt cheap, doesn't taste like much so you need to flavor it for sure. Marinated in gochujang and air fried or baked is awesome
-Seitan is damn near 100% wheat protein, not a high quality protein but there is at least lots of it. Also doesn't taste like much
-Probably the worse one here bc it is much more fatty than protein-y, but chorizo cooked up, then add cheese, rice, cilantro, lime juice and sour cream and it makes one hell of a burrito. Probably no worse than a burger tho, maybe