I think the guy that told you it's "not that rare" was trying to steal it from you.
I try to keep track of the hard-to-find items on Yahoo Japan Auctions, and this is not something you see all the time.
I haven't seen too many of those going for sale.
I'd say it's a "rare" piece.
From the pricing of other hood scoop "covers", it should price out around $100 as a good starting point.
I wouldn't be surprised if it went for auction that the final selling price doubles that.
Mind if I ask how much you paid for it?
-Ted