And it's not just (or even mostly) costs. Nowhere in the world has supply chains anything like the Pearl River Delta. Need the most esoteric component imaginable? There's probably a factory down the road that can supply it, MOQ 1 or millions. It probably has a booth or distributor in Huaqiangbei where you can grab a few hundred today. The US has nothing to compare. US manufacturers can't build those sort of domestic supply chains at any cost.