The latest dealer price for the discs is £25.26p EACH you can get them cheaper by using none dealership genuine parts suppliers @ £23.41p each.
Audi UK price certain spare parts (brakes, exhausts, headlights) with really fine margins as they are trying to increase thier market share of the lease market otherwise you can often get genuine parts alot cheaper than the dealers
For example wing mirror:
Cover - Dealers £31.91p
Cover - Other £24.76p
The glass is much harder as there are about a zillion different ones, blue tint, heated, electric etc etc and prices vary
Cheers
C