Half Price Books Rip off my father rip off your reputation houston Texas

I sent my father to go sell a hefty amount of books and was expecting at least twenty. Because thats what they usually give me. And a reciept but today when my father came home, he handed me a measily $7. I've gotten more for 4 small manga, I wouldn't have gave $15   a second glance but seeing that $7 for 6 hardcovers and 4 paperbacks plus 2 manga drove me to wrte this complaint. They didn't even give him any type of reciept so he can't exactly go back now, I think maybe they took advantage of the fact that he's old and I regret not being able to go today. I never plan on selling my books there again. Ever.