I am familiar with the 92FS but not the 92FS500. I seem to recall I paid about a hundred less for my new Inox a few years ago.
I think closer to $600 would be fair if it is in perfect condition including box, papers and two mags. Just my opinion, but times are changing with the recent developments in the good ole USA.
I am assuming you will be buying used without a warranty. If new, then the price might be good to go.