Google parts first
I also bought my E90 from Tischer, and while I think the sales experience was good, I am not so convinced that their parts are "cheap". While you have to be careful, I think you can find genuine BMW parts on-line for less money at known merchants. One example: chrome exhaust trim. Tischer lists the retail as $64/each (you need two), and their "discounted price" as $51.20/each. A quick internet search turns up several sites that offer these trim pieces for $35/each, or less - same BMW part number.