Book/gaming stores are still REALLY hurting after Paizo raped them over the, "There is no 4.0 in development and there never will be," thing. I have heard of three different stores shutting down after being caught with inventories that were bulging with 3.5 stuff. Paizo was still offering normal prices for wholesale purchases all the way up to the day before 4.0 came out, which is truly crappy customer service. Yeah, the argument can be made that it was their own fault, but, damn... they have to try to crawl out from the hole somehow.
BUT - you are right - a used book that used to sell for the same price is WAY overpriced. Perhaps it is a poor business decision based on the results of a poor business decision.
You might talk to the owner/manager, to see if they'll take less. If I see you there with a $20 in your hand - and you turn to the door, hey, it's time to make a decision about whether a total loss in my costs is worth more than a partial loss.