I actually just made it to the final boss in this for the first time last night.
I think it's a pretty charming game. The music, graphics, and of course gameplay are all pretty sophisticated for a Hucard.
I hate to say it, but the US version has better graphics in my opinion.
To whatever degree myth and hoarding have influenced the price, I can understand why this game would have the highest demand among all the late super-low-quantity US released Hucards.