If the dealership does everything it is supposed to do then the price is a bit more reasonable and includes more than just an than an oil change. It is supposed to include observing a whole bunch of things to make sure the factory QC was adequate. That said, the price does seem high, but so do the hourly rates I've seen lately.
I just had this done too and the price was the same $389 for me. They also do the final drive, what gets me $40 for 180ml of final drive oil from bulk container. What adds up are shop charges, including disposal fees. The dealership is a good size with lots of people they all need to be paid, plus the dealership supports our local BMW club in a huge way so I don't mind paying because the dealership does give back to the club. I live over 80 miles each way, too many of those miles are very high traffic city miles so I do my own service but I do like to have the brake in service done by the dealer. They do go over a lot. They also found a fault with the instrument cluster, they sent this to the mother ship, a replacement is on order. My GS-911 doesn't show a fault. Nor do I see any problem but I'm sure this is a very pricey part plus labor to fix so I'm glad they got it. FYI it faulted 255 occurrences.