My 3.0TDI has been serviced by Audi from new (admittedly this is only twice) but have been quoted Ł500+ for the next major service. A reputable garage will service it using Audi parts for Ł300.
I am not happy with Audi's services anyway, even at the 37,000 service they would not replace the air filter. According to them 3 years and 50K miles is OK on the original air filter.....
If you were buying an Audi would you be put off by a 'mixed' service history? Would you really only buy an Audi with FULL Audi service history? Once out of warranty, whats the point?
Would appreciate anyone's views on this before I make a decision that will provide a better service and save Ł200..... but may potentially cost me in the future.... worry worry