Sukoshi's a friend of mine!
We talked about that game on MSN Messenger...so I believe the game was a simple blue disk which was overwritten with a simple Akumajo Dracula 2 game (I played the game and there's no difference with the "yellow" one...)
At the Famicom Writer Times, shops can deliver you the original stickers for the game you just copied...
So, this game is rare and not...rare due to the game copied on the blue disk with the original stickers and there's probably only a few of "blue" Dracula 2 in the world...but it's not rare due to the possibility to do the same with another blue disk...
For your information, I've bought this one to featherpluckinfilms on ebay for 160$ last week...and I've completed it with the missing items (the plastic box and the collector card)! ^^