The "ST" means it has a stainless steel frame to complement the stainless steel slide. All other SIGs have a frame made of aluminum alloy. The stainless frame adds about 9 ounces to the gun's weight. Otherwise, it's the same as a standard SIG. SIGs are works of art; the "ST" models are heavy works of art. From what I've seen, that price looks about right, but check on GunBroker to see how it compares.