[Klaus]

I think these lenses were never designed to be really serviceable ...
I'm a bit surprised that they even tried rather than simply replacing a bigger component. Or maybe they did, and the replacement part was a dud.
Considering the labor and handling costs, it probably doesn't make any sense to repair a sub-$500 (retail) lens.
Whatever we see as retail price, the production costs are probably far less than 50% - the rest is R&D, marketing, transport, manufacturer profits and dealer profits.