One day, a man walks into a dentist's office and asks how much it will cost to extract wisdom teeth. "Eighty dollars," the dentist says. "That's a ridiculous amount," the man says. "Isn't there a cheaper way?" "Well," the dentist says, "if you don't use an anaesthetic, I can knock the price down to $60." "That's still too expensive," replies the man. "Okay," says the dentist, "if I save on anaesthesia and simply rip the teeth out with a pair of pliers, I can knock the price down to $20." "Nope," moans the man, "it's still too much." "Well," says the dentist, scratching his head, "if I let one of my students do it, I suppose I can knock the price down to $10." "Marvellous," says the man. "Book my wife in for next Tuesday."