A doctor is at a bar one night and notices a young lady at the counter. He approaches her and says, "Hello there miss, pardon my intrusion, but I was curious to know, if someone were to pay you a million dollars to sleep with them, would you?"
The young lady smiles and says, "That's a lot of money, of course, I would."
The doctor smiles and says, "That's interesting, but what if someone were to pay you 5 dollars to sleep with them, would you?"
The young lady says, "What, are you joking? That's no money at all. Of course, I wouldn't. What do you think I am?"
The Doctor smiles again and says, "We already established what you are, now we're trying to establish a price."