I would guess it's the same body as the normal 6 - steel.
As I have understood it the difference between the MPS and the normal 6 is:
- Different interior material/coloring
- AWD system - same as on the AWD wagon? Or constant 4WD?
- ZOOMZOOM'd the hell out of the engine
- Different body kit.
I think he is refering to the Mazdaspeed A-Spec Kit not the Mazda6 MPS. According to the site they are just fiberglass (FRP). JDM products are never inexpensive it seems. And then there are shipping charges $$$!!