My SDL is very reliable it has never let me down. She also always starts and stops.
But I only have to fix a few things every week.
The same can be said for a W140 and I'm sure a W220. All complicated cutting edge cars are expensive to keep going. Heck look at the W116 6.9! It had air suspension in the late 70's! That didn't come back until 1999.
MB's were never ment to be cheap to run they were ment to run for a long time.