We have the smallest Mercedes SUV from ten years ago (the GLK). Our maintenance costs (all routine preventative maintenance) now exceed our purchase price. Yikes!
I bought a 2 year old Mercedes ML350 4matic in 2010, and it has been the most reliable, trouble-free car I have owned. For reference, my first car was a 1959 MGA 1600 Mk II. And it was barely 8 years old at the time.
Just out of curiosity, how many miles have you put on the car? I don't put a lot of miles on my cars. After 10 years I didn't have a lot of high figure maintenance costs for my sporty rice burner. When it came time to replace the high performance brakes the dealership wanted $5K+ to replace them. I had my brakes replaced at the local Farm and Fleet for about $750. If I knew better at the time, I would have had them put in after market performance brakes for around $2K. My biggest cost was insurance over the years.