Correct - the final drive is a weak spot in those years of bikes. Typically an $800 part (last time I checked) for a new or properly rebuilt final drive; fairly simple to replace in your garage, if you are used to working on shaft drive bikes.
They also have dry clutches, mounted in such a manner that you have to split the bike in half to replace. Not something for the new mechanic. ($1,600 at Engle Motors BMW, Kansas City, last time I checked). As with any old bike, service history and being currently ridden are the most important part. With a BMW, having a master mechanic and / or very good BMW MOA club in the area is very helpful.
Would I buy one if I lived in Dodge City, KS? No. Would I buy one in Kansas City? Yes.
Would I love to have one? Yes - they are absolutely brilliant to ride, but brutal when they quit.