[jjk166]

> But what is the opportunity cost for RR to design and manufacture these engines versus devoting those resources to engines for Boeing and Airbus?

Less than what you offer to pay them to divert those resources, which is in turn less than what it would cost to acquire those resources by another means.

> This is more like asking some combination of Intel/AMD/Nvidia to design a custom chip and TSMC/Samsung to build it for you.

Exactly. You don't see Ford building their own fab to make the chips that go in their cars, they pay existing fabs like TSMC to make their chips.