Hello everyone: first there are TWO types of Cutts installations.
First Winchester offered the Cutts as an option starting in 1939. These barrels were forged with the Cutts base on them. Also Winchester hand lapped the choke tubes to thier requirement of the desired choke tube, (Full, Mod., Imp/Cyl, Spreader etc) to ensure they would meet the patterning riquirements of the specific choke. Factory (Winchester) barrels had no choke designation on it, it was left off. (no Full, Mod, or Imp/Cyl etc near where the chamber length was stamped).
The second would be a Full, Mod. or Imp/Cyl choked barrel that was modified by ADDING a Cutts onto the barrel. you will see the choke designated on the barrel and it doesn't have the Cutts base as part of the barrel.
Winchester Factory Cutts are somewhat rare. As tulsey said, generally speaking a Md 12 that has had one ADDED usually drops the price by about half. then again the addition of the standard Simmons rib, means the gun has been REBLUED. So even a Factory installed Cutts gun that has had a Simmons rib installed, is no longer original, thus a shooter classification.
If a person is looking for a Md 12 with a Simmons rib and a Cutts, I can tell you today, Simmons charges almost $400. for thier standard rib installation, a Cutts plus installation $100-$150. But the gun is only a "shooter" not a collectable.
Years ago if one "bulged" there barrel forward of the magazine tube, the quickest and cheapest method to fix it was to have it cut off and install a Cutts or Poly choke. This was cheaper than sending the gun back to the factory for a new barrel or taking it to an authorized gunsmith that Winchester allowed to do this job.
Again choke devices don't appeal to everyone, nor do Simmons ribs. But considering the cost of doing it today, it's cheaper to find one already done, than to do it today. You certainly aren't going to hurt the gun shooting steel shot out of it.
Again knowing what it costs to have a rib installed and a Cutts, $400 isn't a bad price but I certainly wouldn't pay more than that. Perferribly less.
Regards to all!
Dave