Lipped Disk - 200 RS Cup

Had a mooch around the car this morning before it went in for its service (main dealer) and noticed the rear drivers side disk is now lipped close to the centre. What sort of price should I expect to be shafted for when I receive the call in around an hour for a new set?

I know you can get the lip filed off at a local garage for sub £20 but it might be worth investing in new disks as they are the originals.

Cheers.