If you need protein it is not broken down and used for energy. I could be wrong but I didn't think it worked that way. What seems to happen is that excess protein is converted to energy. If you need 2800 calories then you need to consume that many in all the foods you eat. If you need 100 grams of protein and consume 200 grams then the excess 100 grams will be converted to energy, not the 200 grams. You will have to consult a textbook to make sure this is correct.
True that, the protein industry is just crazy. Whey is basically junk left over when converting milk to cheese. It's a waste so it's not even worth 5 cents a pound, yet most company sell whey protein powder (the extraction process is inexpensive btw) about 10 dollars a pound. That's just wrong imo, but gotta admire the marketing behind it all.