You might have seen somewhere a dentist offers free teeth cleaning. Now you go there for the free service while cleaning your teeth the dentist says that your teeth are turning a little yellow and you started worrying about your yellow teeth. Then he offers you to do teeth whitening and you agreed to do teeth whitening and you spend money on that because you don't want yellow teeth. The dentist started working on your teeth and a little while later he says that your teeth has become weak and started shifting. So you again become worried and ask the dentist to do something. The dentist offers that he could fix this with retainers. You agreed to do that and you spend more money on that. On the way out the door, the secretary pitched you for another appointment with dentist six months later at a discount price, so you agreed to book the appointment. So now you see that you went to the dentist office for free teeth whitening and you came out by spending thousands of dollars...