A recent comment got me thinking: in what way could you spend $0.99 that would provide less practical value than purchasing one of my books?
Paying someone a dollar to punch you in the face – This was my first thought. The problem is that a person who's never been punched in the face before would get much more than a dollar's worth of knowledge from this experience. Everyone should get punched in the face at some point in his or her life, to know how good of a chin they've got and to learn how to not freak out in physical confrontations. But if you've been punched a few times, you'd probably get more value from one of my books. So that's a toss-up.
Dropping a dollar on the street – Compared to this, buying a book from me seems like the obvious choice. But being perfectly honest, I'm not that likable. So take all the people you can imagine walking down the street and average them together. If you'd rather that that person have your dollar, then you might be better off dropping your dollar. So this seems like another toss-up, until you realize that I only get 35% on a $0.99 sale (I'd get 70% of 2.99 to 9.99). So you basically have to like me three times as much as this average person you've imagined. Unlikely. So dropping a dollar in the street is almost certainly a better value.
Buying a Brokencyde mp3 – I don't think I win this aesthetic competition, but I'll let you be the judge:
Warning: this video contains disturbing images of tiny men shouting at women. It also might break your brain.