It is strange how 1001 > 638, isn't it?
Interestingly, the ZR1 isn't too far behind on the power to weight topic.
Veyron - 4.41 lb/hp
C6 ZR1 - 5.17 lb/hp
1000RR - 2.39 lb/hp
I assume aerodynamics and gearing have as much to do with why the Veyron keeps up with the 1000RR.
But more important, perhaps:
Veyron - $1,298/hp
C6 ZR1 - $ 188/hp
1000RR - $ 75/hp