The current rarest item I'm aware of in my collection is a great condition, CIB copy of Meteorites for the Atari 5200 at a rarity of 8 both on DP and AA. There's one listed on eBay that's CIB at the moment for $239 BIN, which is crazy. Mine was found in the wild for $5 at a game store that cares more about Final Fantasy and Zelda than Atari titles.