There are dozens of Model 19s floating around on Armslist and Gun Broker that sellers want Model 29 prices for. This weapon is definitely in-line with market value, if not below it. I'd buy it!
Just for reference, two P&R 19 snubs ended recently on Gun Broker. Both had slight handling wear, plain black sights and Pachmayr grips: one got $525, one got $520- reserve not met.
Earlier this year, I paid $500 for a 19-6 snub with Pachmayrs. It ended up being the tightest, most accurate gun I own and even has the best trigger. If the gun feels right, I'd say it's definitely worth $500, and will only appreciate in value.