You make a million iPhones in China. Pay laborers well under the American minimum wage to do so. Then you ship in bulk through a deal with a shipping company.

Or you make a million iPhones in America. You save on international shipping costs. But you have to pay the laborers double to make the product. You have to make sure those laborers are happy and trained to make safe products efficiently. You have to combat labor turnover and comply with US Labor Laws. Basically your continuous labor costs would increase well beyond the savings of a single import deal.

Not to mention you still have to import any resources you need for parts, many of which only come from China, for literally the exact same reason as above. So you still get slapped with international shipping. “Common sence” ok?