Once upon a time a man appeared in a village and announced to the villagers that he would buy monkeys for $10 each. The villagers, seeing that there were many monkeys around, went out to the forest and started catching them. The man bought thousands at $10 and, as supply started to diminish, the villagers stopped their effort.
He next announced that he would now buy monkeys at $20 each. This renewed the efforts of the villagers and they started catching monkeys again. Soon the supply diminished even further and …