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