My previous BMW was an X5 4.4. Never had any issues with it other than regular services. Depending on which service it was due for - cost was between $600 and $1200 (with brake pads). I had it 4 years with 110,000 kms on the clock. Given service intervals were every 25,000k's, it cost me about $3500 over those four years or $875 per annum. Compare that to my Nissan Patrol Turbo Diesel which I had prior to that, each service was around $400 average but that needed to be done every 5,000k's - the comparison cost for the same number of k's would be $8800 or approx $2200 per annum assuming the same mileage.
Now I know from experience if something breaks that shouldn't like the coils fail or the air con packs it in (as has happened in my wifes e46) the repair costs can seem horrendous but you have to balance that with the long service intervals and relatively low annual cost of these.
BMW is still the best made car I've owned. Thats why I purchased a new one and why we currently own two of them.
