Remember that the normal Audi "service" price doesn't include filters, oil change or anything that you might have included as the base "x mileage service" with independents.
I still go to Audi, but better to go in with your eyes open: it was a pretty unpleasant surprise that they even charged me a couple of quid for the washer fluid that I had topped up in the car park before handing in my keys... apparently they check the windscreen washer alignment as part of the inspection + service, THEN check the fluid levels afterwards, so had to refill what they'd used...
Still not as bad as when I took my BMW bike in to have some new heated grips fitted, only to be told that as part of the standard inspection, they had noticed my oil was over-filled, so they had drained and re-filled it at a charge of "£X".... at which stage I thanked them for correcting the mistake they must have made 2 weeks earlier when the bike had been serviced by them (incl oil replacement) and produced the receipt that was stapled to the previous service notes, cheeky b@st@rds even started trying to tell me that I must have topped it up at which stage I pointed out that I wouldn't have the first clue where to start with that particular bike and it didn't strike me as the sort of "vandalism" that I'd expect in either of the locked garages at each end of my commute. Grrr....