One of these sold on e*** recently, for around 60 bucks, but I purchased a new condition two piece Colt Cobra box, with a new condition shroud, attaching screws, and paperwork, on the same auction site, a few weeks earlier...and all for 30 bucks total. The rare few I've seen at gun shows, were priced 20-30 bucks, in various condition. So, like many not so common items, it will depend on where you are, who has it, and how badly any potential buyers want it.
To me, the shrouds only value would be to cover the drilled and tapped hole, in a nice Colt that had the shroud missing. I would never drill a gun that did not have one installed from the factory. But that's my own personal opinion, and others may disagree.