This is from the McMaster campus store:
We recognize and empathize with the students regarding the costs of books so we have introduced the Guaranteed Buyback Program.Please let your students know that if the purchase the above book and return it to the Campus Store by April 27, 2017, they will receive $60.00 (whether the book was purchased new or used). This is 60% of the new book price and 80% of the used book price that they will receive back.