Expensive of course. I owned a brand new A4 for 5 years and there were numerous faults, unbelievable but havind said that it was really fun to drive! if cost is an issue, you'd better consider Japanese cars.
Yes, when it was still under warranty, it would be free of charge for any parts. I've replaced the head lights, city lights, blasters, gear box computer, etc. in first two years. After than, I replaced the main computer, broken oil tubes, rear lock, etc in the rest of time at external garage.