In my case, both a collector and a serious user. Just replaced a slightly cracked "perch bellied" pre 1935 style buttstock on a 1921 field grade M12- nickel steel barrel 28" full- I have owned and shot the living daylights out of this one "Perfect RePeater" and in 15 years, only part I replaced (up to the buttstock) was the hairpin shaped carrier return pivot spring.
I own two Model 12's that I don't shoot very often, so they might be considered in the "collector' range- : (1) A 1939 mfg. 28 gauge field gun 28" solid rib barrel choked WS-2, and (2) A 1949 Pigeon Grade Trap gun with the "Old style milled rib" and a 30" Imp. Mod. choked barrel. I am too cheap to buy and shoot 28 gauge shells when I can shoot a Model 12 20 gauge (1931 mfg. 28" mod solid rib barrel) and accomplish the same thing for a lot less ammo cost. I haven't shot a round of 16 yard Trap in years- clays are a great game, but not the same as shooting barn pigeons in a crosswind, IMO.
None of my Model 12's will be offered for sale while I am on this Earth--so the pricing for used ones on today's market is a moot point.
I recall a F&S magazine ad from the late 1950's- a gent with a field M12 in brown hip boots is next to a railroad boxcar and a huge pile of red Winchester empties- "A lifetime of shooting won't wear out a Model 12"-- Yes indeed!!