Mine was done last week. 1016$ with that el cheapo cover. The gasket alone was changed 20 months ago. So BMW cash in by saving on the plastic version (presumably cheaper to build than in alu) and replacement parts.
I kept the cover to examine it closely and I found no crack or notch.
2007 E90 AW 323i Step | Lowered 1.25"/1" | BMW Performance Exhaust | Debadged | Scangauge II | Style 162 18" & 161 17" wheels & rear 15mm spacers