When I sent my R31 back for repair in the early '90's, I spoke at length with their repair tech. He told me that there were just over 800 R31's produced. The first 50 were kept by the factory for testing purposes and the rest were sold to J.Q. Public. I was actually lucky I had to send it back twice because they sent me a free 30 round mag each time they returned it, so now I have 4 mags.....sweet! They were also working on a 50 round mag for the P30, P31, R31 series, but the AW ban cut that project short. Makes one wonder if there are any of these floating around somewhere.
As for price, I saw one for sale for $1600 about two years ago. I had mine at the local gunshow a while back so I could find a sling for it, and was offered $1200 on the spot by some hombre walking the halls. I really don't know how much the R31 is worth to someone who must have one, but I suspect an owner who doesn't realize what he has may sell it for significantly less due to ignorance. This is afterall a somewhat rare piece that has avoided the "assault weapons" radar to this point. I'm sure low production numbers have something to do with this too.
MG