I couldn't say for sure, I know with most Audi designs a large number of basic repairs for most cars begins with "Remove motor mounts or engine from vehicle" which adds on 4 hrs of billable shop time if I remember right. My assumption is that the Phaeton is built on more of an Audi platform in terms of overall design and intended audience being higher end clients, this would lead me to believe that the combination of frequency of known issues along with cost of parts and labor would make it a no go in my book regardless of my income.

Mercedes is getting sloppy over the last 8 years or so, again I love their cars but their known issue list and build quality is growing to the point I would probably not have them at the top of my list.

BMW seems to just keep plugging right along with no more or less common failures than they ever have, they are spendy on repairs but you are looking at higher end models so this is expected. I would run each of these through a combination of Consumer Reports reviews, Forums relating to make or model specific looking for common issues and headaches as well as talkign to owners of these various vehicles on the forums to get a solid pro and con list. Separate the fanboys from the honest owners with rounded views on the cars they own.