Foundries are incredibly (insanely) expensive to run, and Samsung Electronics runs more than anybody but Intel. Given the sheer volume of business that Apple do

Foundries are incredibly (insanely) expensive to run, and Samsung Electronics runs more than anybody but Intel. Given the sheer volume of business that Apple does with them, it's likely that Samsung literally cannot afford to drive Apple to a rival foundry without either ruining their foundries' financials or massively driving up the component costs for their own products.