How "average" is the box? Any tears, rips, etc? What flaws?
What about paperworks?
As far as I am concerned, the King Poseidon giftset is almost all about the box and the Japanese paperworks.
If these are not in acceptable condition to you and complete, I wouldn't recommend because you can get a complete Piranacon for half that price. However, with that being said, $650 is still a pretty good price for that giftset. It used to be a lot more expensive.