Yeah, it's a big myth that BMW and Mercedes parts are super-expensive. Now, if you buy an M5, that will be true, but for a garden-variety 3-series, not at all. Honda and Toyota parts can be very expensive and routine maintenance can be just as expensive for a Honda as for a BMW.
We've owned Subaru, Honda, Acura, BMW, Mercedes, Mazda and Porsche products. Take out the Porsche parts prices (yowza!) and I would say that the Acura had the highest parts and maintainance costs and the Mazda were probably the lowest. For some reason our 626 had good access to good jobber parts at really low prices.}