It was on some audi/bmw forum. They said owning a german car out of warranty will cost you about $3k-$5k so set that aside every year. Idk about an official source though.
For the record there are quite a few Mercedes, BMW, and Audi lease deals that will cost the owner less than $5k a year. Something to consider is although they have higher MSRPs the cars are often discounted much heavier to get butts in seats. It isn't uncommon to see leasees paying 10-15% under MSRP for their vehicle. And if a leasee holds out until year end that figure can easily jump to 20+% for a previous MY vehicle.

