"It seems you trusted that nice boy far too much!  Suppose I'll trade eleven cherries for a banana, or a banana for fourteen cherries, but when it comes to trading a banana for twelve or thirteen cherries, I neither accept or reject either of those offers.  You can't pump infinite fruit out of me that way, even if I trade by those rules consistently, and the rules don't correspond to having any single price of a banana in cherries."

"It seems you trusted that nice boy far too much!  Suppose I'll trade eleven cherries for a banana, or a banana for fourteen cherries, but when it comes to trading a banana for twelve or thirteen cherries, I neither accept nor reverse either of those offers.  You can't pump infinite fruit out of me that way, even if I trade by those rules consistently, and the rules don't correspond to having any single price of a banana in cherries."