From the (possible) original:-

Churchill: Madam, would you sleep with me for five million pounds?
Socialite: My goodness, Mr. Churchill... Well, I suppose... we would have to discuss terms, of course...
Churchill: Would you sleep with me for five pounds?
Socialite: Mr. Churchill, what kind of woman do you think I am?!
Churchill: Madam, we've already established that. Now we are haggling about the price.

(This is a very old joke where the participants vary dramatically from each telling. It's very unlikely though not impossible that the joke originated from Churchill)