I have a 2015 650i but RWD it’s an amazing car I don’t regret it will be getting a M6 tho in a couple years but maintence can be pricey with what u do I had to replace a lower radiator and a couple more items it came out to 5K but I had a warranty to cover me so I didn’t pay anything but if u don’t then yes it’s expensive to repair parts
So when it came to my car “breaking down” it was my whole radiator and a rear flex disc + another item I forgot but regular maintenance it’s too pricey in America where I’m at I always do 5W-40 euro full synthetic ever 5-6K miles but can last 7500 my last maintence was oil,air filters, alignment and new wiper blades came out to 600 bucks in total and my tires I got the top of the line non run flats came out to 1500 bucks in total for all 4 including insurance on it tires don’t wear easily maybe more on the AWD but on my RWD it’s fine