For anyone who hasn't, do yourself a favor and check out thomaspin's web site. A great resource. Thanks again for all the work Thomas.
I purchased my 86 420 sel in November 2001. It had 80,000 and I bought it from a repair shop who had changed the engine because the timing chain broke and trashed the valves and pistons. So beware of that. My car came with a used 125k engine with new chain and guides. The car now has 130,000 and I get those admiring comments from whoever gets in the car and sometimes from strangers. To this point I do all of my own maintenance which includes, new brakes and rotors $200, oil and filter change every 3000 to 5000 miles (3000 if I have the time) a new voltage regulator/brush set(see instructions to replace on thomaspin's web site), new left window regulator (gear stripped at the top) new radiator( the top neck was of the old non metal reinforced style, Tires. I guess about $1500 total. Not bad for 50,000 miles
I absolutely love this car. When I bought it I was really looking for a 140 but got a great deal on this one ($7000). The cheapest 140 I could find at the time was about 15,000. I still like the 140 and look forward to it someday, but for now my old 126 still takes me on 300-500 mile trips without problems and impresses my customers when I get there. She is white with red leather.

As an owner of a 99 S420 W/ 50000 miles. I would look for one in the best condition regardless of the mielage. It may be a better idea to buy one w/ 60000 than one with 30k as many of the bugs have been ironed out by the previous owner. I would not even look at any non-99 models as the evaps go south prematurely. Get a V8 S420 or S500. Try to find an S500 Grand Edition (collector car)

Make sure that you get the following options:
Sunshade, Parkatronics, Heated Seats
and definitely no S420 w/ rear axle control because the shocks are very expensive and don't get one with ADS either.

Before you buy the car, have the dealer do a prepurchase inspection. If the car has been neglected, expect at least $1500 worth of maintenance and wear and tear items. If it needs any repair expect no less than 1000. W140 is a car that if you need to ask how much is repair, you probably can't afford to have one. I have '01 S600 and the W220 chassis is a much cheaper car to own than any W140.