People some time confuse price with rarity.
Sometimes?
Just about 99% of the auctions that I see, even here in Europe, for games like Mega Man, Castlevania, Probotector/Contra, etc, always say RARE, super hard to get, etc....ahh well.
As for the hardest boxes to get, I just find deals on games I don't have yet and pick them up, so I don't check eBay for longer periods for any one game and therefore don't have much of a clue
Your list looks pretty good, though, based on what I've heard