Again I will post this. Swamp weighed his m3 and WITHOUT a driver it came in at 3600 or so. (his is weighed with a driver and notes he is about 180 pounds so subtract that from the weight.
Same scales same day show the c63 at 4000 pounds without the driver. It had a full tank of gas however and the m3 had a quarter tank so for comparison lets make c63 about 3950 since half tank of gas is about 50 pounds.
So 3600 v. 3950? That is 350. No way to argue that.
Then if you look on the merc website, they list BOTH the c63 coupe and sedan weighing nearly identical at 3930's so you cannot say the coupe weighs so much less than sedan like some says. So its probably a good 300 pounds difference.