Yes you can say they are overpriced in a sense but you are paying for the quality and R&D and some times the name alone will add a premium. I just wouldn't put Megan racing in the same category as Akraprovic or Eisenmann.
The E92 M is a very special car and deserves special parts but thats just my opinion but everything is so expensive so i do understand your point of view.
But like they say you have to pay to play!!