I wouldn't reject a gun that had a well done stock extension, but it would have to be very reasonably priced with an eye toward eventual restocking. I've heard figures of something like $800.00 or so for grain painting to cover a stock extension, and share the same concerns as Stan that it is nothing more than a surface treatment. That kind of money would go a long way toward restocking many guns unless you were paying top dollar for upgrade high grade wood and labor.
I'm surprised that no one has mentioned the better alternative of doing a butt-transplant on a gun that still had a sound head and grip area and good checkering. I don't have any idea what a good stock man charges for that option, but it is something on my list of future projects for a couple guns that have old deteriorated recoil pads and less length of pull than I prefer. There is a very good description of the process in "Shotgun Technicana" by McIntosh and Trevallion.
