The bookstore, what a ripoff!

I went to the university bookstore today to sell back my books and try to salvage some of the money I spent for them. This semester I spent $350 on books and the bookstore wanted to buy them back for $27. I was so shocked that I had to ask if that was a total. Then, to top it off, when I said that I would just keep them, the lady looked at me as if I had personally offended her. How rude!