The key bit is getting it for a price your comfortable with.
Mechanically they will be fine its the bits around the engine that are still key bits, the perishables. Ive spent about 10k on my Z4M since I bought it its only got 73k but its 15 years old. Having had a really good condition coupe in the past and knowing how well it drove and getting it back into that state is costly.
Depends how anal you are. Granted ive been going through it with a fine tooth comb, I didn't need to spend that on it. If I was just sorting the important bits I think probably 5k would have been sufficient. Its when you start thinking about all your suspension components, deciding to sort the rear subframe out, springs, dampers, engine/gearbox mounts, Vanos, bearings etc The parts aren't expensive but the labour is.
The benefit of buying a high miler is I would be less worried about having a go at it myself and it would be a bit of a project but as a reliable car I would spend more money and buy a lower miler.
I think the problem is now these are getting old it doesn't matter if its a low miler or a high miler all those perishables will need doing sooner rather than later.
If your just looking for a car another factor I always think is important is how many miles will you do, if your doing 3-4k a year then a high miler is probably more palatable but if your doing 20-30k then its inevitable that the car is going to need much more attention quickly and the cost benefit analysis slides the other way.
You could easily spend the difference of a high vs low miler on a few big items. That being said once they are done the part will do that milages again.
I used to be in the camp of not having cars above 60k but ive completely flipped that view and as long as the car has been looked after.... its a car after all and is designed to do miles lol