Apple didn't need to hire "cheap labor" to build those iPhones. In Apple's high-tech operations the labor costs are a very small piece of the costs of producing and shipping the phones.
There was a fascinating story in the New York Times a while back about the challenge Apple faced in producing the special glass that was used in the first generation of iPhones. Apple actually got the lowest bid from Corning to produce the glass, and Corning was going to manufacture the glass iPhone faces in one of their facilities in upstate New York -- which happens to have some of the highest labor costs and most ridiculous labor regulations anywhere in the U.S.
Corning lost the bid because they couldn't upgrade their facilities fast enough to meet Apple's needs. It was going to take them at least 3-4 months to deal with an endless series of New York State and Federal environmental, construction and development permits.
The Chinese company that won the bid had their factory up and running in less than a week.
No manufacturer ignores labor costs, even Apple. Saving a dime per unit translated into millions of dollars in increased profits down the road.
Jobs said these kind of tech jobs would never return to the US, and he was right.
One is the cost of US labor, but the big one (as you mentioned) is the enormous cost of complying with US laws and regulations.