Once upon a time a man appeared in a village and announced to the villagers that he would buy donkeys for $10 each.
The villagers, seeing that there were many donkeys around, went out 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 donkeys at $20 each.
This renewed the efforts of the villagers and they started catching donkeys again. Soon the supply diminished even further and people started going back to their farms.
The offer increased to $25 each and the supply of donkeys became so scarce it was an effort to even find a donkey, let alone catch it!
The man now announced that he would buy donkeys at $50 each! However, since he had to go to the city on some business, his assistant would buy on his behalf.
In the absence of the man, the assistant told the villagers: "Look at all these donkeys in the big cage that the man has already collected. I will sell them to you at $35 and when the man returns from the city, you can sell them to him for $50 each."
The villagers rounded up all their savings and bought all the donkeys for 700 billion dollars.