It depends on the car!
I've had my 1976 240D (W115) for many years. Some years maint. runs only cost for oil, filters, fuel additives, etc..... general maint. stuff. Some years are different, like with any car you will have major expenses every now and then. Last year I dropped about $1200 above normal, but the year before was only $100.
These cars are well engineered, but do require regular upkeep.
You could buy a well maintained Benz and sink another $5K on repairs next year. On the other hand, you could drive it for ten years without anything but oil changes, valve adjustments, and tires! Remember, it may be a Benz, but it is still a used car.
This is a judgement you will have to make yourself. Most of the guys (and gals) on this forum do their own repairs and enjoy doing it... maybe that's why we have older cars.... hmmmm...
Whatever your decision, we are here to help you out.....