Once when I younger and more gullible I bought a book from an ad in the back of a magazine about how to get rich. When I got the book I was very excited.
The book basically said to write a book about how to do something then sell it. Which of course was exactly what the author of this particular book had just done.
At first I was pissed. “Just write a book he says!” what a rip off! But since I spent 10 bucks on it I went ahead and kept reading. His book did go into great detail on how to find print shops to print your book, how to buy ads in magazines and newspapers to sell your book including a lot of detail on how to haggle with ad sales people to get good advertising rates. Then there was a whole chapter on how to organize your mail room, tips on sorting incoming mail and how to process your book orders, how to package your books cheaply and still protect them from damage and how to get the best postage rates when mailing your books.
For some reason all these years later I still debate with myself, was I ripped off or not?