This also happens in practice because the super experienced 10x guy has not balanced a RB tree or some similarly 100% solved std library algo in practice for 20 years and won't even get the job. The young 1X guy just got of uni and had to do it as an assignment just a year ago so they will employ him first, as they have no repeatable way to differentiate between a resume BS artist and the real McCoy. It costs everyone but that is automation practiced on a corporate scale.

Or they spend the +30% and get someone who’s just as productive or 10x less productive. It’s not a magic price performance formula.

It may surprise you, but the people I worked with the last few years strongly preferred very senior developers.

So on the contrary one could argue that they are cheaper (yes ;)) but also can learn something new. Also I think that very junior people bring some kind of enthusiasm into teams. I guess the right mixture must be there.

Or they can get two competent testers. :)

Source?