Repair costs so low I bought another one!
When I purchased my first '85 300D I had the same fears/concerns. I have since been so impressed with the "maintainability" of the car that I purchased an older one with more miles on it than the first, and with no major concerns.
I figure with the average lease/purchase monthly cost of a car to be about $300 for anything decent whatever I do not spend on maintenance I am "saving". I would estimate my annual repair costs to my 300D at around $500, including fluid changes. I do most of my own work and do not sweat the little things so these cars make sense to me.
Hope that helps.
'85 300DT--215,000 miles
'82 300DT--255,000 miles