How much can i sell my .40 caliber smith and wesson sigma?

My first handgun was a .40 Sigma. I bought it for 350 NIB and I fought to get 200 back when I got rid of it. The manager at the gun smith I bought it at was only going to give me 150 for it. A week prior he said 200 and I held him to it. Of course I put the money right back into another gun (Beretta Px4 Storm). I only had the Sigma for 4 months. Constant jamming issues.