Of the two Dual Model Kit kits (Optimus & Bumblebee), the more expensive one has been done in translucent plastic, and is a promo set with the Bluray TF3 movie in Japan.
The set is in hand now, and some initial pics of the un-assembled figure has been posted here.

I think it ended up being double the price of the regular Optimus kit, which was already at about AU$100-150... depending on the source.