I think it depends on the individual who buys one, and on the commemorative itself, whether they hold extra value. If the individual has some connection to what the gun commemorates, it will be worth more to him than someone without that connection.
As to the gun itself, I think it depends on several factors. Was the commemorative made available to the public from the start, or was it only available to a certain group initially? How many guns were made in the commemorative form? Seems like if only ten guns, each would have more value than if there were a thousand more like it; if a thousand, each would maybe have more value than 10, 000. Anything special about what was done to them? Nickel on a model where nickel was not otherwise available, or exceptionally rare? Plain, or highly engraved?
I own one commemorative; I bought it because it represents my state's largest law enforcement agency, The NC Highway Patrol. This commemorative has a couple of firsts; it was the first time a Model 29 was used as a commemorative. It was the first time (and so far, only) that the design on the gun was acid etched instead of engraved or roll stamped. This commemorative was issued for the 50th Anniversary of the NCHP, and that was 42 years ago (1979). Another eight years, they can add a 100th anniversary issue, maybe. The revolver used is a M29-2, a desirable pinned and recessed version, and is nickel plated, which brings a premium value to even a non-commemorative M29. There were less than 1200 made (each is individually numbered), and initially, they were only sold to currently serving State Troopers, or retirees of the NCHP. That adds a little provenance, I think, if you can discover who owned it first. (I haven't found out yet). Maybe I'm building mine up because I believe it does have a value greater than any other M29 you could have ordered back in that day. Maybe it doesn't, but I'll hang on to it and pass it along. So far as I know and can tell from close inspection, it has never been fired. There is an unsubstantiated belief among collectors of this commemorative that NCHP requested on the order for them that they not even be test fired by S&W, but that is apocryphal. I haven't decided yet whether I want to shoot it, so far I haven't.