Gents,
In Poland all ball joints can be rebuilt.
I have recently rebuild a gr 4 ball joint ( for 150- GBP a pair ).
Now its is better than new, though for a civilian car the material used would be different and thus the cost would be half.
I guess in countries where the parts were simply not available for decades the mechanics learned how to rebuild old parts, and now with all qualities of steel easily available the quality of a rebuild one is better than the new one.
I am afraid , that once we get as rich as you guys in UK the generation of master experts will die off

.
In Poland relatively large number of cars are "10 year old plus private imports" mostly from Germany, France and Belgium. Young people want "brand name" cars for peanuts with replacement parts half free.
BMW until recently was on the top of the demand list. I am not sure why it is appealing to young guys but until recently all they wanted a black BMW. ( Note until recently all Polish mafiosos drove black BMW's, now they drive Bentleys). Nowadays you can but a BMW series 3 for 1500 Euro. If you pay 1500 Euro for a car you will not go the BMW dealer for spare parts. Most replacement parts can be found on a local junk yard. Usable ball joints cannot be found on a junk yard so to fix a problem the driver goes to a garage that specializes in rebuilding ball joints...
Incidentally, these garages are increasingly involved in rebuilding old cars as well as producing special parts for performance sports cars. Maybe they will survive this way.

Miro