[SD ///M4]

Discounts on M Performance Parts can be found on eBay offered by genuine BMW dealers across the country. BMW of El Cajon, my local dealer, recently offered the CF Rear Diffuser for the M3/M4 for less than $999. I know the parts guy and he told me he would sell to me at that price, so I picked it up when I was in for my 10K service. I've been watching the price of that for the last year and it was the lowest price I had found anywhere.

Various dealers offer discounts on shopbmwusa.com. You have to "Pick a center" and there may be discounts that pop up, depending on the item. I bought my MPE and my CF Rear Spoiler from Advantage BMW in Houston for 25% off.

Edited to add: getbmwparts.com (Tischer BMW) very often has very good prices on M Performance Parts.

BMW NA also ran a very-limited time program last year where you could buy certain BMW parts, including M Performance parts, from any BMW dealer, at any price, submit the paperwork, and receive a Visa gift card for 25% of the purchase. I applied that to my MPE, and other parts that I bought during the specified time period, and received 25% back. This brought the price of the MPE from $4,400 MSRP down to $2,475 ($4400 x 0.75 = $3300. $3300 - 25% = $2475 for a total discount of 43.75%.