Aged books

Today this guy came in with a paper bag full of OLD books. Like so old they smelled horrible and were yellow. He wanted me to buy them back from him. So I stood there and typed in about 20 ISBN numbers. Some of these books are so old they don't even have ISBN numbers. So I finally finish and I total the amount he was going to get. Now here's the thing, it was 11 wholesale books... but it only came out to $6.75!!! All that work for a measly $6.75! Each book was worth $0.25, $0.50, or $1.00!! I kept expecting him to say, "oh don't worry about it. I'll just THROW them away..." but noo... Seriously these books STUNK!