are egg shells a good, cheap source of protein?

Good morning ladies and gents, I’m currently trying to find cheap sources of protein to add to my diet, and I remembered that a while ago, an Uber driver of mine claimed that he ground up egg shells and added the powder to his protein shakes, he also stated that they’re high in casein but upon further research, I’ve found that the majority of the protein is in the membrane of the egg, not the shell, and that the shell is mostly calcium carbonate. Just wondering if anyone could provide some insight, or possibly recommend some cheap sources of protein powder.

Thanks in advance!

are egg shells a good, cheap source of protein?