Foxconn employs about 1.2 million workers in China. In Shenzhen and Chengdu, a combined Foxconn workforce of 500,000 provides labour for Apple Inc. Daily wage is ~$5 per employee. [https://www.facing-finance.org/en/database/cases/working-con...]

Napkin math if you were to move 500k workers to the US and paid them $100 a day instead of $5 a day it would cost you $17B a year.

Would be interesting to see how labor per unit is trending to determine if manufacturing is actually getting more automated and at what rate.

The main thing those numbers are telling you is that Foxconn is really big.

I think your link is also relying on data which is several years old, this is more recent and listing average hourly wages of $3.60 in China:

https://www.cnbc.com/2017/02/27/chinese-wages-rise-made-in-c...

But that's still less than a third of $100/day.

The real question is whether the required number of employees is off too, which if the numbers are from years ago and the theory that automation is increasing is true then it would be, and then as you say, how that plays out in terms of labor per unit.

In what world do you pay a skilled American $12.50/hr? And that is before considering benefits.

You’re absolutely right, I was being unrealistically conservative. In reality that many workers would almost certainly unionize and average labor costs could easily be $250-$300 a day or more.

The main reason modern manufacturing is in (mostly south) China is the ecosystem! For electronics specifically, you have a tightly woven network of suppliers, factories, part distributors, logistics companies, and lots of local expertise tying it all together, as well as lots of established relationships and processes that keep it running smoothly. A factory, however highly automated, does not run in isolation. Of course you can build that kind of ecosystem elsewhere, but that's a 3-4 decade project and requires enormous investment at high political and financial risk (which is what China did in the 80s with the SEZs).

Regulation. It's not that easy to buy land, build a building, hire and fire people. If this is confusing, try buying some land and building a building.

Also the supply chains are all over there so the lead times and communication are vastly better.

Here's a cynical view: a human is cheaper to "develop" and "program" than a fully automated production plant in most third world.