Support the cause
Isn’t it the case that one man’s trash is another man’s treasure? So, even though his wife had assured him no one would buy his old books, he had a hunch someone would want them. Or perhaps they wouldn’t want the books themselves, but they’d buy them to help him prove his wife wrong.
This guy quickly sold out of his previous books thanks to his clever sign, “Prove my wife wrong, buy a book.” He didn’t claim that people would read the books; he said they’d buy them, and he was correct. We’re guessing that many men would like the chance to prove their wives wrong for only $5.