You're not taking into account the type of usage that BMW have to Toyotas. Toyotas are usually driven by non-car-enthusiasts, and people that do care about reliability.

BMWs on the other hand are enthusiast cars, driven quicker, modified more, raced in tracks, etc. Obviously the reliability is going to suffer. I'm pretty sure that under normal usage, they will endure as much if not more than a Toyota.