Apple almost certainly has entire production lines at TSMC that they effectively own. I don’t really think bringing chip fabrication in-house has any immediate benefit for them.

We can observe with Apple’s pricing staying stable that they have some of the best supplier arrangements in the industry.

Apple doesn't own TSMC. TSMC is putting Apple in the back burner in favor of Nvidia and other high margin companies.

They are literally being limited by TSMC (as well as the DRAM makers) because they don't have their own fabs.