Sorry to let out your secret Blunt but I happen to know your parts business is not your livelihood and I'd like to help these clueless saps out, so I dont have to keep reading 'I got buttf'ed at the dealer today...' threads.
What Blunt has going on is nothing special. I became good friends with my dealership parts guy and started getting wholesale pricing(60-70% of retail) by default. He then let me in on something I wasnt aware of in case he was to ever leave BMW. Simply go down to your county courthouse, pay 20$ and get a 'License to do business' permit. Name your new company 'Insert your last name here' Performance Shop. Go back to BMW, show them your new license and ask to setup a wholesale account. Voila, you now get wholesale pricing. Now a few caveats. First, they wont ship or deliver your parts to you unless you actually have a legit business address. Second, there are different tiers of wholesale pricing based on the volume you purchase. So you wont be able to entirely match Blunt because Im betting he gets a bigger discount because he seems to move quite a bit of product. One last benefit is that you will be able to order parts for your friends and get them the discount as well once you setup your account.
This is basically what places like Maximillan are doing except they take it one large, work intensive step further and setup a website in order to sell to the public.