Many, many writers-- including those published by major publishers-- are supported by friends and family who provide beta-reading and coarse proofreading help.

Buddies get the book free and before everyone else; they're not expected to fully, deeply edit the book, but just give feedback about the most glaring things. This can be a reasonable deal for all involved-- I'd gladly substitute in a book from a buddy for my nightly reading and highlight it and give him feedback.

Of course, I also help my friends with minor professional questions gratis, too.