That might be a little low if condition were mint. Not so much if it's got holster rash or other understandable issues.
Remember that the gun shop has to bring the gun into their books ,resell the gun AND guarantee it ( and make make a profit.). That used gun, when sold, may also be in place of a new one they already have in stock.
Bottom line: Most shops I've worked with offer 55% blue book on a flat buy , 65% on a trade. ( Again, condition is EVERYTHING) As an alternative, many will consign the gun and sell it for you at 15-20% of the sales price.