I agree with you. However, there are some who are clearly willing to pay the extra for the kudos of driving a M3 or a C63. Plus I think that the price gap is getting closer between these cars. All these types of car will be difficult to sell and as they get older, reliability becomes a big factor. I tend to read that M3/C63 should not be bought without a warranty, which can cost up to a £1k a year.
Hmm in saying that I have been quoted about a grand for a Lexus warranty!
The C63 appeals to me with that glorious exhaust note, but factoring in the other costs, as a compromise the ISF is the one for me.