Has anyone else had there alternator go at 100k . Auto electrician said it’s very rare and cost so far for replacement is $2500 nzd to replace

1979 5dr, Diesel, 5 speed golf.

The car has had a reconditioned head, runs well.
Has had GTI lights & grille fitted + wheel arch flares.
The paint has small blemishes but in overall good condition & has polished up well.
Inside is very clean and the car...