> At what point will Apple try to build/buy their own foundry?
As soon as they are tired of having money.
It isn’t just the cost of building Fabs, literally their entire supply chain is based on being Fabless, and changing that is ridiculously expensive. They have some amazingly skilled chip designers inhouse, but even so many aspects of the actual manufacturing side of the design process were not done at Apple, although they exert an outsized influence.