Chap walks in. "I'm looking for a copy of George Bernard Shaw's "The Apple Cart - I don't suppose you've heard of it."
"Yes sir, I believe we have a copy in our plays section."
"Really, how marvellous - its out of print, and I've hunted high and low for it. How much is it"
"It's a first edition sir, from 1920, in a decent dust wrapper - it's £6"
"Oh no - I don't want to pay anything near that - do you have anything for a pound ?"