If you read his post its cheaper for M style, the price he quoted above is with colour coded archs also which bumps the price up
So long as the paint doesn't peel off there is no worries with Warranty work being needed on the aero kit.
Hell maybe M style could do a better job of painting it than BMW, the number of peeps who complain about stone chipping on the Aero bumpers (although my cooper Aero front was practicaly spotless

)