I know this thread is a few months old but ..... sounds like something in the $500 range is pretty reasonable. However, there's a lot of Ruger Commander variations in finish and caliber. Can't imagine that $500 is too high for any of the variations but may be low if it's some special edition or finish. Did they make one commemorating Navy Seals or the NRA? If so, those may be more spendy.
My Commander is a lightweight 9mm. Bought it a month old from a local guy who'd put exactly 50 rounds through it. Still had the box, manuals and all that. I didn't even try to dicker at $500.00. Heck, I put another 100 rounds thru it just yesterday along with my G43. They're the 2 semi-auto's I shoot the best.