I have experience with 686's in the 2.5" variety and what I have found drives the prices of them up is a few things....

1.) Older dashs or no dashs in 2.5" are'nt easily found
2.) No MIM parts
3.) No lock
4.) Original finger groove combat grips...some sellers add $150 to a $500 gun because of these grips.

If given the choice between an older 686 with combats and a newer 686 with the lock, MIM parts and a Hogue grip, I would take the older one everytime, even if it were a bit more.