All the ones I've ever seen were conversions; and BAD conversions, at that.
I think there may have been dedicated cabinets, but I've never seen one.
As far as the rarity of it, I've seen a few for sale, so I don't think they are THAT rare.
As far as the value of them, I've seen them not sell on ebay at relatively low prices.
If they were that valuable, someone would have snatched them up, and had just the boardset shipped.