I had a chat/quotes with several specialists around Christmas time for chain replacement on my 2012 320d Auto (N47) and the prices ranged from £1500ish to well over £2k. Also a few things worth bearing in mind such as....
-
the n47 has 3 chains, 2 tensioners, and several plastic chain guides and some of the garages I spoke to gave me the option to select what I wanted changing. To change all of these like for like is an engine out job.
- I was informed that
BMW developed a split chain kit that allows them to replace the main chain only without removing the engine but was advised that this is not a favourable option (and most likely a quicker fix solution to get noisy cars well out of their warranty period).
Hope that helps!