Which model? There's letters after the 106. U, UR, CR, F, FR. U is short. 8.5 or 10.5" barrel. C is 16" barrel, with a combo gas block so you can form1 it and cut it back to 12". F is 16". R is for the side rail. If you find one NIB, you're gonna bend over for it. No doubt kvar still have some NIB and is slow rolling them out onto gunbroker to get maximum dollar. Gonna be $3k. More if you get in a bidding war. Maybe $1300-2300 for a used one.
A couple things to watch out for. Some of the 106 had incorrectly milled selector stop plates under the mag catch. It made the mags lock in wrong and they had feeding issues.
10.5" U size had a fake booster. The gas block has no threads, and the fake booster is pinned to it. If you want the correct muzzle setup, its gonna run you $400 after parts and labor.
And there are some ban state models that are a little harder to convert to correct format that the non-ban state models.
I have a UR and CR currently. Very nice. 10/10. I had the 106F with a railed top cover and sold it off. It worked fine, but people were paying more than it was worth to me.