I have two Ruger Mini-14's. Both have 185 series Serial Numbers for the 1 in 10 twist barrel. One is set up for Coyote Hunting (and it has worked very well for that) and the other is set up as a Tactical Carbine. The one setup for Coyotes has a Barrel Harmonizing Muzzle Break and a GLass Bedded Stock. It will give Sub 1 inch groups for the first 10 rounds which is generally more than I need. The Tactical version gives groups of 3 to 4 inches at 100 yards. Not Great but OKay for Combat. For the Hunter Magazines I use the Factory 5 or 20 round Boxes. For the Tactical I use ProMag 30 round Thermolds. BTW, barrel re-crowning will enhance a Mini-14 or Mini-30's accuracy very nicely. (I have a Mini-30, as well!)
Value may depend upon which Serial Number Series you have, to some who know the Mini-14, like myself. I value the 185 Series and before for it's 1 in 10 twist barrel as it will shoot most bullet weights up to 62 grains, as will the 189 Series, which has a 1 in 9 Twist barrel. The 189 and later Series Mini-14's will also handle bullets up to 75 grains. The 187 Series which has a 1 in 7 twist barrel is only good for bullet weights of 62 grains and higher, and best avoided.
Most used Mini-14's are in the $300 to $400 range, depending upon condition.