Contracts are what they are, but they don't preclude discussions like "if we honor this as-is, it leads to a situation where we have no incentive to value you as a customer".
Firm orders years in advance are in general far more valuable than much more expensive orders today. With the years in advance orders you can make plans around them.
That might be the reason for rumours of higher storage (1tb). An excuse to charge 30% more to not only offset increased costs but to increase profit margins.
If not that means that Apple will have a competitive advantage on price with other manufacturers that utilize TSMC.