I'd get a second opinion from an independent repair shop. Do not ask them to inspect the differential. Don't even mention that word. Let them find the cause on their own without being swayed by what someone else said.
BMW is one of the least customer-friendly manufacturers in the world and their parts costs are just one example. They also have a lot of tricks built in to force you to go to the dealership, but often other shops can work around that. Differentials are typically repaired, not replaced, unless the shop doesn't have anyone qualified to work on them. (They are very tricky to set up correctly). You would normally only get a new assembly when the car is still under warranty. For older cars you'd get a rebuilt assembly to save money. If there really is a problem in the differential, I'd be nervous about getting a used one that might have the same problem or develop it later.
You didn't elaborate on the noise or when it occurs, but in general differentials cause very little trouble and outer CV joints are a common cause of a clicking noise, particularly when turning and accelerating. You'll rarely hear that at higher speeds. That is typically heard in parking lots. It's less expensive to install the complete half shaft assembly than just the outer joint. A rebuilt assembly will cost between $50.00 and $150.00 for domestic cars. You might expect one for your car to cost double that, but even with two hours labor to replace it, that's a lot better than what you were quoted.
If the second shop also comes up with the differential as their diagnosis, find out exactly what they think can cause this noise and what type of repair they recommend.
Tuesday, October 15th, 2013 AT 12:40 PM