I agree $500 is fair, however, I got mine $550 shipped/insured couple yrs ago. It is far less common than the ubiquitous 686 or GP100. Wouldn't call them rare though. Other forums has mentioned that parts for it could be harder to come by, since the SS has been discontinued more than 20 years.
For .38 spl +P and +P+, I like my shooting the SS better than my GP100. Full .357Mags are better in the GP.
One thing, the GP is more accurate and I discovered the cylinder throats on the SS are .357 and .358 on the GP. Maybe I will ream out the SS cylinder throats to .358