You're only partially correct. Apple doesn't need a fab. Apple needs a systems integrator like Foxconn and it's MUCH cheaper (order of magnitude max) to setup an assembly plant than a fab. But yes, I suspect subsidies would make even a $100m investment profitable.
I was using chip fabs as a point of comparison in regards to the scale of Apple's investment. It was chosen because HN readers are more likely to be familiar with the cost of such manufacturing plants than, for example, those associated with automotive manufacturing.
I agree that Apple doesn't need a fab. It doesn't need a manufacturing facility in the U.S. either.
They might eventually need one (or a non-Samsung partner) considering their increasingly contentious relationship. Intel would definitely fit into the overall progression of events[1].
