[jjbiotech]

Because quality increases when Apple repackages Chinese components in a shiny white case.

[esmi]

Definitely.

Apple should add many QA steps filtering out the vast majority of bad parts. First there would be incoming QA on any received shipments. And any well run assembly line contains many check steps to make sure the unit has good constituent parts. This way you don't burn good parts farther down the line on a unit that was never going to pass. Then there is out going inspection and burn in testing.

All that testing increases overall quality and value.

[lacampbell]

Nail on the head. Some people have a very naive view of manufacturing, QC and supply chains.

[jjbiotech]

QA/QC isn't exclusive to large companies. DIY hobbyists can do the exact same thing.