This is a Car and Driver M2/M2C weight difference breakdown which is kind of more theoretical.
https://f87.bimmerpost.com/forums/sh....php?t=1566186
This is a guy that weighed his own M2 and M2C configured the same way which is information that's straight from the horses mouth. The M2C weighs about 110 lbs. more. The 788M wheels on the M2C weigh about 17 lbs. more than the 437M wheels on the M2. That brings the weight difference down to around 93 lbs. If all the extra cooling mods etc are taken into consideration, I think it was 93 lbs. well spent.
https://f87.bimmerpost.com/forums/sh....php?t=1529257