Even if the bore and chambers are nice,,,$100 would be my top price in that condition. ,,,and that would probably be a generous offer at that.
Being the poor refinish that it is,,you are buying a hammer and trigger and some internal parts.
An awful lot of time and labor could save it if you have any thoughts of doing the work yourself. I've done more than a few over the years.
Just satisfaction in the job, or a learning experience in how to do it are the ways of looking at it.
It wouldn't be worth the investment to pay someone to do it,,even a simple re-re-blue .
It may be a good shooter as is,,but don't pay any more for it than that.
Decent M&P revolvers are around in the $200/$300 price range. Even the occasional Victory still floats by $300. It won't be exc'lt condition finish wise,,but you shouldn't have to pay that for a poor re-blued example.