I 100% agree with you on this point, MSN.
Here's an example. I own a nice Rolex Oyster Perpetual. It's not perfect...it came with an incorrect caseback and I had to find a salvage caseback with the correct case reference. But the movement is excellent and keeps chronometer grade time. As you know, older Rolexes are not dated by movement serial number. Instead, they are tracked by case serial number.
Since Rolex has never released the records of which movement serial number went with which case number, it is impossible to determine if a particular movement is original. I guess when Rolex serviced watches back then, it would be common to swap movements if there was a major problem and fix it later.
As a result, I've been told that my watch is worth about $1,200 as is, but I were to remove the movement and sell it separately, it could fetch up to double that amount. Why? It is a caliber 1030 automatic, which was used in far more collectible Rolexes like the early Submariners. These can go for $20,000 and more at auction. If one has a broken 1950's Submariner, it would be much easier to buy my movement and drop it in, than to source the parts needed to fix the original movement. The salvaged parts from the original that will work have a decent value on their own, since many of the parts for these older Rolex movements are almost unobtainable.
Since there is no way to match the movement serial to case serial numbers (without the original COSC documentation -- very rare),
most Rolex collectors would be satisfied so long as the correct cal. 1030 movement is inside and properly working. Therefore, working movements from less valuable Rolex variants are worth far more in the marketplace than complete watches.
Supply and demand, that's how the market works.
gatorcpa