Ive found very little information on this other than it may be limited to 5 drops.
Aye, you can't predict the "x" factor. I just call them winning lotto's when you find one of themI would trust Manticore, he's very knowledgeable on value of rares. The discrepancies come when you find a collector who is particularly interested in collecting that item. Then the skies the limit on how bad they want it, and at what price you are willing to give it up.