Around here, at the local shows, gunstores and pawnshops in the greater Seattle area, the used .357 models with a 2.25" barrel seem to go anywhere from $ 325 to 400. I don't see a lot of the spurless hammer models, but they generally go for $ 25 or so higher than a spurred hammer model. Also of note, is that I just don't see a whole lot of used SP-101s, in comparison to the plentiful supply of used S&W snubby revolvers up here. I think this tends to keep the Ruger prices up.
I am often amazed at the local WAC shows to see some of the vendors, separated not more than 50 feet apart, selling the exact same handgun with anywhere from a $ 25 to $ 75 price differential. This applies to firearms in general, not just the SP-101.
And boy, if I could find a new SP-101 for $ 269, I would buy two or three of them just to stock up. If I could find a good used one for $ 250, I would snatch it up. When I see new SP-101s in retail stores, it is usually for $ 450 to 500. In the Seattle area, we don't have the 'big box' gunstores that serve to keep the prices down. A Cabela's opened just last month in Lacey, but it is a 140 mile round trip and $ 20 in gas for me to get there. We have no Bass Pro or Gander Mountain, and the few Sportsman's Warehouse stores seem to carry way more S&W revolvers than Rugers.