There is so much more to this car than just the price. I took one for a drive round a track here in New Zeland (we have two) and the difference over the "normal" FD2 is leaps and bounds.
The suspension is much more track focused then the street FD2R (for argument's sake I'll call it that) and of course there are the differences in the brake pads (FD2RR runs a Mugen pad as opposed to the normal pad run in the FD2R), exhaust note, interior, the list goes on.
A lot of development work went into the RR and as a result it laps a full 3 seconds faster round Tsukuba circuit than the FD2R (from memory, maybe someone can find a more accurate time, but makes the FD2R look slow).
But is it worth the money? Have you seen how much the carbon bits on that car are worth? You couldn't buy an FD2R and convert it to RR for the price, and I'm not just talking about the body, the engine is AWESOME. For that money I would expect REAL carbon fibre in the doors, not carbon style, but for a car that fast who would be looking at the dash when you're thrashing it? The RR I drive didn't have a steering wheel like that, it had a real sweet leather MOMO job WITHOUT the horrible red inserts, I would say the original steering wheel has been "taxed" somewhere along the way, it'd be worth a fortune!
Dunk is right though, for that price I'd have an NSX, but store a Mugen RR in a garage for 20 years and it'll be worth you retirement fund for Honda, who'd love to buy it back...