Well, are there American companies like a Foxconn that have the infrastructure to assemble 40-50M iPhones in a quarter? Apple doesn't actually build the factories and hire the workers. They outsource the work to Foxconn. Where is the Foxconn equivalent in US. Also, people are only comparing the wages of a single Chinese to an American. In terms of iPhone assembly, are American as efficient as the Chinese? Are they willing to put in as many hours? If not, there might be a need to construction MORE assembly lines to have the same production and THAT would increase cost greatly.
People love to say they would be willing to pay more for an American made product. Well, Mac were made in Cali when PCs were made in China, Taiwan. Which computers did Americans end up buying and why? PC because Macs were too expensive.