It's not just about money ... The original article came from the NYTimes URL link but there is a good analysis also at businessinsider.com.

The real reasons Apple makes iPhones in China, therefore, are as follows:

Most of the components of iPhones and iPads — the supply chain — are now manufactured in China, so assembling the phones half-a-world away would create huge logistical challenges. It would also reduce flexibility — the ability to switch easily from one component supplier or manufacturer to another.

China's factories are now far bigger and more nimble than those in the United States. They can hire (and fire) tens of thousands of workers practically overnight. Because so many of the workers live on-site, they can also press them into service at a moment's notice. And they can change production practices and speeds extremely rapidly.

China now has a far bigger supply of appropriately-qualified engineers than the U.S. does — folks with the technical skills necessary to build complex gadgets but not so credentialed that they cost too much.

And, lastly, China's workforce is much hungrier and more frugal than many of their counterparts in the United States.