[ghettoimp]

It does seem like TSMC has strong leverage since it would take Apple a lot of time and work to move to a competitor.

On the other hand, the incentives seem pretty well aligned. TSMC presumably makes a lot of money when Apple is successful and sells a lot of chips. Having a customer that is demanding and willing to pay for huge volumes of bleeding edge parts helps TSMC build on their lead. Having early access to the best process helps Apple differentiate, and their business model gives them the margins to afford all of this.

Anyway, I don't see why either side would want to really change this setup.