What is going on with these Sub anchors?

[Rotorhead]

Like others here on the forum I check out Rolex items on Ebay. But when it comes to these anchors, the prices that I see that sellers are getting for them just amazes me. It seems that the 200m ones are bringing the big money. I know that collector interest generates the prices, but from what I have read here, there is no certainty that they are even legit! I would think that the only real ones are the ones that came with the watch and I can't really see those owners parting with them.