i think the answer would depend on a few things (which perhaps others can weigh in on):
- when looking at product line profitability, how does BMW allocate R&D and other overhead costs? one might argue that M vehicles consume more R&D resources than others
- what is the volume, by product line? i would think for the higher volume M cars, BMW could eke out a few more margin points as they "optimize" stuff during the production run
- what price will the market bear for a given model? Example: the e92 is most likely not too different in production cost from an e90, so the additional upcharge for the coupe will go straight to margin. the M6 GC may be another example of this