There were two end-of-the-semester textbook sales when I was in college.
I went to the first one with my used Luotuo Xiangzi, required for Intro to Chinese Literature, but the book was denied after they scanned it.
Then I went to the second fair. They scanned it again, and told me the system shows 0.25 dollars. I said that's okay, so they handed me a quarter and the receipt.