I own a 2001 S600. I love the car. It has luxury features like ventilated seats, parking sensors, Bose audio, fold-in mirrors and more...
The tandem power steering hydraulic suspension pump failed. Got a new OEM Mfg. one for less than a thousand (compared to $4,113.00 quote installed at dealership). A hydraulic line ruptured and I had the line repaired for $40.
None of the maintenance items are that complicated. Not too expensive if you don't mind shopping. Example O2 Sensor Mercedes Benz Brand $320.00 Bosch $90.00.
The automotive service industry sees big dollar signs when you pull up in an S600. The folks who believe that an S-Class is expensive to own and maintain could be right if comparing to the cost of five-year-old Toyota. The sales price of a 2015 S600 is about $170,000.00 Plus options; first year depreciation $61,000.00 according to Edmunds. I own my S600 for less than $10k after purchase and maintenance items. Is that expensive? The five-year-old Toyota probably costs that or more, but the Mercedes S600 is definitely more enjoyable.