m75 ........
Everything's negotiable! If it survives the weekend, I'd offer the shop owner $400. total (out the door). This bid may be closer than you think. Negotiating out the door, IMHO, is the best approach. If he doesn't accept that offer, he may settle for $450. or somewhere in that range. It all hinges on what he has invested in the piece. You'll never know until you test him. With that said, the asking price is still reasonable, based on your description. Make the offer anyway.
A good example of this was back around 1970, a casual acquaintance said he wanted to sell his 4" .357 Colt Python that he purchase new a couple years prior, with only a handful of rounds through it. I told him I was interested, and we arranged for a meeting. It was perfectly mint, and Colt's "royal blue" finish back then, was absolutely superb. He was asking $400. and I told him that I was interested, but that it was realistically worth half of that. I told him to think about it, and give me a call. It was worth a wild shot, just to plant the seed I thought, and it worked. He called me the next day and said if I'm still interested, I could have it for $250. Done deal. If you don't negotiate, you'll never know. That purchase began my collection of Pythons in all available factory offered barrel lengths, except the 3".
Attached are photos of the above mentioned Python as it is today, with the addition of genuine Elephant Ivory target grips custom made for me around 1972. It remains as pristine today as when I first purchased it. Colt's "royal blue" finish has held up great, and is still the best "factory" finish I've ever seen. Good luck! Let us know the end result.
Shadow SD