Howdy
The market for these guns is fairly volitile. There are ALLOT of the guns out there for $7-900 dollars. They have been for sale for a LONG time. If you wanted to sell it fast a good price would be around $5-600 depending on the acual condition of the gun. The holster that you stated is worth some money by itself and anything with Detonics on it seems to sell for good money on EBAY. Unless you have a Ultra rare model pistol a good place to start with value is the blue book of gun values. Hope this helps...
L8r
Conley Janssen
USMC 87-93