To be honest, to me it sounds like there isn't even that much profit even if we just consider grain to glass. I'm totally uneducated about the subject but it seems like you need quite a lot of grain for beer, and beer is quite cheap... Larger brewers make sense but for smaller ones, either their beer is super expensive or I'm missing something!

I don't drink alcohol so to be fair my knowledge is mostly coming from friends getting trashed on cheap Pabst Blue ribbon lol.