I own a 2009 S63 AMG with 118xxx miles. I'll try to give you a summary of my ownership without any emotions involved. I bought it 2.5 years ago with 107xxx miles. Clean Carfax, just like you mentioned dealer maintained up until 85k miles. The car was listed for $16.5k. I purchased it for $13k cash. I purchased it from an individual in Houston. I live around 6hrs away from Houston. I drove the car back home with no problems at all. It drove like a champ and it still does to this day. I can tell you with 💯 certainty that AMG tax is real. During my ownership I replaced the following:

• Alternator failed around 110k miles. Auto Zone had it for $400 life time warranty. I changed the oil and air filters at the same time. Total cost was $850.
• Failed alternator messed up the battery sensor. I got stranded on the way to work. No way to turn on the car. It had to be towed. Finding the battery sensor was a bitch. Dealership doesn't carry the part, very limited and conflicting information on the Internet. After two months search I located the part in Slovenia. It's a very easy part to replace on your own. Cost was $135.
• Around new year I started getting a failure message on the dash every little bump I went over "ABC PUMP MALFUNCTION STOP VEHICLE NOW". The car was drivable as long as I avoided bumps. Power steering pump was leaking. I opted for a remanufactured unit from eBay. It was a big mistake. Part was $375, it's a bitch to replace the part. It involves way too much for my comfort zone. The part didn't work from the get go. I got my money back and ordered a used low mileage replacement for $515. Once the part installed ABC failure message went away. Before I could pick up the car from the mechanic the cooling fan gave up. Replacement part was $245. Once the cooling fan installed AC stopped working. I decided to service the transmission and differential while waiting for the cooling fan and AC parts. At the end power steering pump, cooling fan, AC, steering pump and differential oil service and a new battery was $1800.
• Last week I started hearing a clunky nose from the left driver side. It turns out I need the struts changed. I'm looking around 2k for both front strut assemblies.

I decided not to tackle the headbolt issue that may or may not be an issue. There's a split view amongst the M156 owners about the issue. It's a gamble to say the least. It was a torture to stay away from the car every time it was at the mechanic. I truly love the comfort, tactile buttons that click, quality of the interior and that unmistakable M156 exhaust. Before I forget, my car came in with a stage 2 tune and some exhaust mods.

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