It's not the price, I've heard the Sylvania 2721 lasts much longer than the OEM bulbs. Something about the filament in that one doesn't handle vibrations too well or some shit. If I can't find it at Home Depot I'll definitely hit up the dealership.
'02 ///M5 Imola Red / Imola Red '09 335i Alpine White / Coral Red
'04 E55 AMG Brilliant Silver / Anthracite
'96 318i Alpine White / Black
'01 330Ci Titanium Silver / Coral Red
'96 328i Jet Black / Black