The Cowboy has become a collectible piece because collectors and/or investors think it's worth the investment. As far as a shooter goes...they're fine...the problem is that they're simply not an SAA in construction, finish, etc. For its original MSRP and purpose the Cowboy fulfilled what was intended but the market decided otherwise. I think it deserved a better fate but Colt rarely has stuck with a product that didn't sell well immediately. Maybe it should be resurrected and be better finished at a price competitive to the Italian copies and it could find a better market...but I doubt if the millennial crowd will be interested...it's not made of plastic and have tacticool accessories hanging of it. It's a design for traditionalists and that seems to be a declining breed.
I had both a 5 1/2" and a 7 1/2" Cowboy...still have the 7 1/2" NIB. It amazes me some of the dollars they're bringing in but the market doesn't have to make sense. When my wife and I begin down-sizing in earnest within the next two years mine will go on the market but for now I'm hanging on to it...unless the market value gets too high to resist.
But as a true collector's piece...I think values are overblown but those who can't find or won't pay the price for a SAA will buy the Cowboy because it says "Colt" on it. If they set the price that high I can't hold it against someone for selling one at that price.