Gattlingun - any time you try to sell a gun back to a gun retailer, or a pawn shop, you're going to get bare bones minimum for it. They then turn around and mark it up as far as they think they can, Wouldn't matter if it was a Glock, Kimber, or Taurus. You don't really think he's going to turn around and sell the gun you just traded in for $225 do you?
EDIT - What you should try to do is sell the gun privately. Of course check your state and local law on this, but you will make much more money on any gun if you sell it this way. I'd imagine you could get around $325 to $440 for that gun, depending on the condition.