One day, a man walks into a dentists office and asks how much it will cost to extract wisdom teeth. "Eighty dollars", says the dentist.

"That's a ridiculous amount!", the man says. "Isn't there a cheaper way?"

"Well...", the dentist says, "if you don’t use an aesthetic, I can knock the price down to $60." Looking annoyed the man says, "That's still too expensive!"

"Okay", says the dentist. "If I save on anaesthetics 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 for next Tuesday."