The royalty check that he gets for book sales on amazon is barely enough to cover his cost of shipping to amazon and printing expenses. I'd be impressed if it covered the cost of printing the guide book, being pictures and colors on every page. Not cheap, even in bulk.

Royalty checks are really only lucrative if you sell THOUSANDS of books, like a best seller or if your book was really cheap to print and you charged an arm and a leg for it. (see above paragraph) Many book sellers (target is a good example) will charge you a stocking fee, which cuts into profits or royalties and I know a few that will charge you an unstocking fee, meaning if they decide to discontinue stocking your book, you have to refund they for their current stock.

Yes, you can get the book cheaper elsewhere. Are you a jerk, no. Are you supporting the efforts of the author, maybe...but probably not. It's all conjecture.

You don't self-publish a book to get rich or famous. You do it because you love the book or the subject matter. How much do you love the hobby?