If you went with a set of cheap flowmasters you can get this sound. Mufflers are cheap and can be welded in for even cheaper, or have custom piping made. I've done that for all my other cars. Seeing a catback exhaust pipe in the 1k-2k price range just for bmw is outragous. There is no difference between cars. Its just bmw's (Tax) That I'll never pay for.
Or you can go muffler less
Although this is not our model this does sound good too, ive always been a huge spintech fan and this would be a very cheap mod to do. Its a straight 6 with turbo, so its probably a pretty close sound to the 335i. These Mufflers are maybe $300 for both, then $50 to $100 for install. hmm i'm starting to really like this sound maybe ill test it out sometime this summer.