They can’t use the slave labor if they did. Foxconn has a terrible record of labor abuse and Apple doesn’t care.
Foxconn is not slave labor.
Compared to the US, their wages are low, but compared to the rest of China, they are pretty good.
They work 40 hour weeks and overtime is capped at 60 hours per month.
There are no children working in the factories.
Apple has regular inspections of Foxconn facilities to make certain that they are compliant with their contracts, which insist on, among other things, no child labor.
If you, as a business owner, had the choice between paying someone $2.50 an hour or $7.50 an hour, which would you choose?
Maybe, just maybe, the regulatory climate in the US has driven jobs overseas?