That looks a lot like a yellow spoiler again in that last photo!
The TTMall listing doesn't mention an extra piece in the set either... so pure voodoo transformation?
Or it could be an older photo added by mistake (like when Ramjet first went up with one and was taken down shortly after)

And retail is indeed 12000Y+tax here... damn. No mention of diecast, rubber tires or anything fancy, so it's all on the parts count i guess! It looks good but it better be for that price!