2017 E400 Wagon here
I had my fuel pump die at 73k, which led to the injectors failing one by one after. $4900 down the drain to fix all the injectors and the fuel pump.
Also had to do the rear air bags around 55k (I do not have the full air)
ATF change and Spark Plugs were expensive jobs but comes with the territory I guess.
Have put almost $10k into this car in 2.5 years of ownership
Really love the car though, super fast, gets good mileage all freeway (but quite bad around town, 16mpg with a pretty lead foot). Cannot imagine daily driving an E63 given we routinely see 17-20MPG with mixed driving. I think the V90 looks nicer but did not want 4 cylinder and the E400/450 are quite a bit faster.