I think MB means business with the C63 AMG, it has been hailed as the best AMG ever, and they are definitely going for the kill.
I somehow believe that the pricing will have impact on the M3 sales- we have to wait and see on that one.
Most people here in the US are sold on HP and Torque so I won't be surprised if people start rationalizing along the Price/HP to justify the C63 over the M3.
If I can recall, the C55 AMG was more expensive than the E46 M3.