I agree with most that exhaust prices for the m3 is a bit expensive. The thing that bothers me about eisemann is that it's just a muffler and doesn't include piping to get rid of the really bad crimps in the stock piping.
If it included piping like the rdSport, I probably would of purchased it already. But instead i'm in the boat of wait and see.
On a side note, lexus just released an aftermarket exhaust for the IS for ~$1.5k , sure it's not made in germany, but even if it's made in china or korea it still has to past lexus standards.