Other books that are of marketable value may be sold at a price established by the used book company. The Bookstore has no control over wholesale prices, publisher prices or publisher new editions. Your professor readopted the book for next term. We already have a gazillion of 'em in our bookstore, so we can't use it here. It isn't needed here, but it is needed on other campuses.
Demand determines the value.
The new edition is in, so the old edition is out. Your book looks like it's been through a tornado.