> Once you have a team full of experts, you're now spending two programmer hours to do every bit of work that could have been done in one programmer hour by a single expert.

You’re forgetting that it’s impossible for any one person to keep all the details of even a medium sized code base in their head.

I imagine the initial “planning” phase of implementing a change would benefit heavily from pair programming because it avoids the issue where you write a bunch of code to find out that it doesn’t work because of this one detail that you forgot.

For the learning (“knowledge transfer”) aspect, though, I think you’re right that it’s possible to reach a point where writing the actual code (not the design) as a pair is not worth it.