$500 is a good deal.
The 19-3 was the next to last last pinned & recessed version. You didn't mention what barrel length it has and the only track I have is for the snubbie. The Blue Book shows "Add $9 for 4 in. or $14 for 6 in. (disc. 1996) barrel." Snubbies seem to command higher prices these days. With all that in mind, here's my track:
Smith & Wesson 19, 2-1/2 inch barrel. Revolver in .357 Mag. Blue Book of Gun Values (36th Edition) indicates between $325 in 95% condition and $650 in 100% condition for this gun. I have 127 recorded prices for this model gun from $395 to $1055 over a period of 6 Yrs 5 Mos ending September 7, 2016. The average price as of that date was $619. No refurbs, no refinishes, regular sights. All represented as 95% or better. No distinction for engineering revision, if any, no special editions, no distinctions for box, papers, tools. Current or last MSRP is $457. The last 10 prices I have for this model since 12/19/2015 range from $594 to $825 averaging $670.
The data I have suggests that 68% of the sales were from $501 through $737. You can see that $500 is at the lower end of that range.
I have a 19-5. They are real nice revolver.
So, the average used price is still going up. If you get beat up to sell it, you won't lose anything, in my opinion. May even gain some.