I bought a set of OEM E70 glossy black kidney grills from an ebay seller (keshav246)for $175. From ebay I linked to his website:

http://www.auctiva.com/stores/viewst...270&styleid=12

By contacting him directly I got a slightly better price.

They came new from a dealership in New Jersey in about 3 days. I haven't seen cheaper for the OEM, but there are matt black aftermarket grills on ebay for less than $100. I haven't read any reviews of the aftermarket brands.