While I do not mean to argue with Mike, I do feel like I need to show a little different perspective... For members like Mike and Nathan, who been around the forum for many years perhaps there are a lot of factors to effect the price when choosing a firearm. But for a newbie (like me and, I assume, OP as well) options are very limited.
I just bought a beautiful Model 66 and so it happens that for last couple of months a looked for k-frames (19 and 66) very closely. So, where can I get one? In the drivable distance from me there are four or five stores, but only one with decent selection of used guns. Well, they did not have neither model. So, the only place left is an Internet. And I found only three places, where there are a lot of firearms for sale online: Guns America - dealer based and almost always overpriced. Gun Broker - perhaps a decent place, but an auction. Arms List - classifieds where you can get a good deal on the good firearm if you deal with a decent private seller.
The prices on these sites dictate that $600 for Model 19, while on the higher end of the spectrum, not way out of line...
But if there are more good online placed to buy guns, please share, as we (newbies) definitely could use this knowledge. And thank you in advance.