I'd like to add that some parts are bundled by BMW into a kit that's given its own BMW part number (e.g. the Cold Weather CCV package) and some websites create their own kit bundles (e.g. VCG). Make sure you know what's in the kit first, and there's at least one site that was charging more for the "special price" kit than for the individual parts (hey $15 is $15).
Finally, check out the comments here on customer service. The cheapest price isn't fun when you get promises that are never delivered. And read the small print like "upon an approved account" - whatever that means.