I always thought it was a good deal if you fit in the CF bucket seats and were okay with a 4 seater.
Someone in the thread above us just paid 131k for a 5BW with all the CF stuff. That's only about 10k below a M5CS.
The M5CS already comes with the exterior CF, the CF seats, the CC brakes, and also comes with CF in places the 5BW doesn't (but wish it did), like the roof, hood, and I think trunk.
It's the only sedan I've seen best the 5BW in comparison tests (motortrend, Evo).
I had no interest in the M5 comp, but if the 5BW didn't exist, the M5 CS would be the top pick.