Good lenses are expensive, we all know that. I expect that when I purchase a lens that is will be of decent quality and construction.
I don't expect it to be invulnerable while I use it to fend off an attacking cougar...(the feline kind)...but I do expect a decent amount of forethought in engineering.
I have a read a few posts about people dropping their Sony 70-200mm and having it split apart, both the f4 and 2.8 versions. I chalked it up to bad luck or a bad drop. Now after reading the excellent Lensrentals blog (If you don't follow it you should)...not so much.
It seems that some engineer thought it would be a good idea to join the two halves of the lens with a ONE MILLIMETER ALUMINUM PLATE!
Anyways go read the Lens Teardown of the Complicated Sony FE 70-200mm f/2.8 GM OSS.