I was selling secondhand books at the flea market . I got into an argument with a customer. He wanted to buy The Pocket Book of Harry potter. But he said it was too expensive at 35 cents. Other paperbacks were selling for ten or 15 cents each. 
 I pointed out that the book was selling good. Harrypotter was a good book and it wasn't expensive at all . He said it was a matter of principle. Finally, I agreed to sell him the book for 15 cents. Triumphant, he paid with a $10 bill. "Keep the change," he said.