That quip was over cost of labour specifically. The broader point was US no longer had the manufacturing base or expertise pool to manufacture advanced Apple products at scale or timelines of modern release cycles at all, i.e. Cooks observation that PRC had enough tooling engineers to fill multiple stadiums vs US a room. The entire point was that cheap labour wasn't what was keeping Apple in manufacturing in PRC.
10% is many billions every three months. I don't think it's wise or ethical to manufacture in countries that have human rights violations but there's nothing ethical about a corporation.
No longer the case obviously but more importantly, Apple studied themselves and found they were only saving 10% in costs? This makes no sense lol