Looking for a cheap source of protein? According to www.mensfitness.com, some of the most protein-packed sources that are also the most economical are eggs, canned tuna, and peanut butter. Eggs are an excellent source that is relatively cheap. For less than 2 dollars typically, you can get a dozen eggs which translates to around 72 grams of protein approximately. Canned tuna typically goes for less than a dollar a can and typically contains about 30 grams of protein. Peanut butter is also fairly cheap at around 3 dollars a container which provides about 114 grams total. For a little bit more, you can upgrade to almond butter which has an even healthier protein in it.