Your mechanic may be a good alternative to these other guys that are around.
Who is he and where's he located?
Was that 270 for the rotors just for labour or parts too?
To get pricing on most BMW parts, go to www.bimmerparts.com
... this will give you the going US$ price.
Multiply by 2 to get approx. final CDN pricing to you.
I actually get most of my parts currently from FCP Groton in CT.