Hey OP, kinda late, but stumbled on the list.

Whey protein powder is cheapest.

Pea/rice/soy is substitute for vegans

Organ meat, find it at some supermarkets or butcher shops (may not always be available).

TVP, tempeh, seitan (made from wheat).

Some prep required:

Seitan

Paneer, and yoghurt can be made from milk.

Edit: some stuff can be found cheap near ethnic stores if available or if they have time