A man goes to the dentist with bad toothache.
Having checked the tooth, the dentist tells him, “your aching tooth will have to come out, but don’t worry it will take just five minutes”.
The man asks the dentist, “How much will it cost to pull the tooth out?”
The dentist tells him it will cost $90.
The man is furious, “$90 for just a few minutes work?”
The dentist replies, “I can extract it very slowly if you like”.
Image used under a Collective Commons License from https://commons.wikimedia.org/wiki/File:A_man_suffering_from_Toothache.png