There is allot of reading here and I got to page two and stopped and all I want to say is that at the end of the day a car is a machine, a machine can last a life time if you look after it and make sure its properly lubricated with good quality oils etc etc. Sure you will need to replace wear and tear items and sensors will go here and there, but that is what comes with owning a car.
and 81k is not high mileage, to say that is high mileage is ludacris.
What I will say is that at 100k on my 525, it cost me a bit of money to fix things cause a whole bunch of wear and tear items went, water pump, thermostat housing, radiator bottle got hair line cracks, power steering pressure hoses, power steering rack, belts, pullys etc but once those are all replaced then car was good as new and will probably go for a long time again, the new owner of my car should be very happy as that car is sorted for another 100k easy, my friends E46 325ci hit the same mileage and the EXACT same things went on his car except for the power steering rack, all sorted now and the car is good as new.
Wear and tear items will always go, dont not buy a car because you might have to replace a water pump down the line, thats a silly mentality and if that is your mentality then don't buy a second hand car, just stick to buying brand new cars and get ripped off to the max!
Thats my 02c