Or, the Parable of the Broken Window
The fallacy of the onlookers’ argument is that they considered the positive benefits of purchasing a new window, but they ignored the hidden costs to the shopkeeper and others. He was forced to spend his money on a new window, and therefore could not have spent it on something else. Perhaps he was going to buy bread, benefitting the baker, who would then have bought shoes, etc., but instead he was forced to buy a window. Instead of a window and bread, he had only a window. Or perhaps he would have bought a new shirt, benefitting the tailor; in that case the glazier’s gain was the tailor’s loss, and again the shopkeeper has only a window instead of a window and a shirt. The child did not bring any net benefit to the town. Instead, he made the town poorer by the value of one window.