A lemonade seller and the businessman.

A lemonade seller was standing in the hot sun selling lemonade. A customer, who is a businessman approached him and asked him the prices.

"$3 for a full glass, $30 for 5 empty ones."

Astonished, the businessman asks him, "What is that supposed to mean?" The seller remained silent.

After giving it a thought for a while, the customer bought 5 full glasses of lemonade, giving the seller $15 (3×5). He drank all of them quickly and showed the seller 5 empty glasses, "I got 5 empty glasses only for $15, though the cost is $30. You see, what dirty tricks we businessmen are capable of!"

The poor lemonade seller says, "Sir, I am an entrepreneur. You see I made you buy 5 glasses for no reason at all?"

Edit : Ignore bad grammar please.