Would I be wrong in assuming that along with your moderate driving habits you have good maintenance habits? In other words, do you have the engine oil and filters changed out at say 5,000 miles (it’s a diesel and all kinds of nasties build up if you go much further), including the diesel filter itself (you don’t have to, it’s just a nice precaution)? If you have maintained your car well, then it is likely that you had the automatic transmission fluid checked and changed. VW says your transmission fluid is meant for a “lifetime fill.” What is a lifetime fill? Some people say it is 100,000 miles; others say it’s 125,000, and others say it’s 40,000 to 60,000. The answer is this (it’s my preference): 40,000 to 60,000 miles. As I said, it’s my preference, but I think 60,000 is the maximum mileage for transmission fluid. Granted, it is an older idea but it is still sound, IMHO.
So, with the foregoing good habits established and with your VW at 280,000 kms, it’s not unreasonable to expect things to start breaking down, for no apparent reason. Age does have a lot to do with things. At nearly 300,000 kms, thing happen. For example, your transmission likely has had a build up of various deposits over time. It is not unusual for this to happen as dirt and other debris will settle out of transmission flow and begin to buildup at various points. Over time, those deposits, if they are on turbine vanes or the impeller, the clutch pack faces or bands or on the gears. The deposits may be really tiny, but they do have their effect at causing transmission imbalances and other damage. Over time, too, items like the valve body and the associated check valves may become clogged or damaged and even internal galleries can be plugged, each of which can lead to more damage. All of this is just plainly associated with breakdown over time.
With all of this said, the figures you were quoted are pretty good. Indeed, I would like to have a fully rebuilt unit installed for $2,800, if I could get one. The $3,400 price is also fair, though it is tending toward the high side.
As for your comment about remanufactured versus rebuilt units being the same, here’s a hint: they are.