No camshaft replacement on mine, and it's been over a year since my service. I however took the car in right away when I heard the noise. It might well be that if you can get the car in and repaired early, that you might not need a new cam. I don't think that all dealerships try to rip everyone off, but rather that they aren't as all-knowing about the cars as people seem to think they should be (which is sad, but I suspect it to be true). This becomes a bigger problem when the customer doesn't know much about cars either.
Basically, just sit down and talk logically with the service dept about the problem. Remember that many places would rather fix the issue once and have it over with rather than have to deal with an irate customer whose car has to keep getting brought in for service for the same repair.
BMW : Sine qua non
Mods: Blacklines | Rear Seat Power Outlets | Rear Fog Lights | Ashtray Garage Door Opener