That is really interesting, because producing them in China would make much more sense business-wise.
My money is on Apple "producing" nMP in USA being a marketing stunt and real bulk for worldwide distribution being manufactured in China.
No it doesn't, this is high end tech manufacturing, not making a $5 plastic chair.
Modern electronics circuitry have to be machined assembled or drawn. They're getting small enough that it's really difficult to have a human solder the chip to the board at a point where you can guarantee QC. You have a lot more yield loss with human assembly than with machines (which are almost always perfect), and quite frankly there's some part of the process that humans just can't do anymore. What you're looking at are really just a lot of QC people and engineers to make sure the assembly machine works.
Then count in the cost of international transport for something this heavy (and yes, it's heavy for it size), and the cost adjustment may not be as much as you would think. When apple move their production oversea, shipping was dirt cheap, ever since 2008 that hasn't been the case anymore. I can't barely ever ship anything UPS or FedEx without costing at least $10.
There's also a lot of issues with having new industrial processes leave the border, it leave the company much more vulnerable to competitors. The method of manufacturing and assembly here are trade secrets, everyone one of their competitors would have it in an instance in an uncontrolled environment like China. You should read up on the nightmares of how many U.S. manufacturers suddenly find competitors putting out exact clone products with the same quality soon after they go to China, even in low and medium tech, never mind that this is the cutting edge of high tech microchip manufacturing.
Going to more machine manufacturing and relocating the factories back to the U.S. is actually a very smart long term play on Apple's part.