The risk that TSMC doesn't deliver on node improvements / deliver the relevant SoCs in the required numbers.

And if you think that risk is small / nil I would point you to Intel's recent track record.

And just to point out that Apple actually does bear the risk you've highlighted as Itanium was a design (which Apple does) not a manufacturing failure.

There is also risk that sufficient consumers do not want to buy Apple’s products at a sufficient price premium to offset the price premium that Apple paid to TSMC.

For a specific recent example of this risk we can look at Nvidia who put down huge deposits for N4 wafers and now doesn't have enough customer demand for those chips.

Good point!

> Oh no, the company that never failed a delivery might fail the delivery! Such a risk

You could say the same thing about Intel until they blew it with 10nm. Who knows what the future holds

Exactly.

Also blaming Intel's process problems on Itanium (discontinued 2011) is - well an interesting perspective!

One risk comes from the long lead times of chip design and production. They are committing to a design and process and hoping that production can occur on time and in the right volume to meet there needs. That is not a certainty and a delay could be very expensive since product releases are tied to the new chips.