But there are other kinds of high achievers who should not leave because, after all, talent is talent.
You don't say, "Bob wrote 70% of our product, and he's head and shoulders above the rest of the team, so he's got to go!"
You should say, "How are we best utilizing our in-house talent? Does Bob engender resentment from the lesser programmers? Maybe Bob should have the role of chief architect, and get Bill to be team lead since Bill's more of a people person."
It's complicated, and every case is different, and the size of the company is also a factor. Part of the art of management is the ability to get the most out of each person on the team. It's hard, it takes years to learn how to manage, and it's not for everyone.
Technology work isn't exactly like basketball. In team sports, you have to work with a team; it's not like you can just play the game all by yourself. The whole point of participative sports is that everyone has to participate.
But in technology, often it's the solo contributors that drive innovation by making a brilliant but messy system that the regular guys/gals have to clean up and maintain.
Once in a while, you see a brilliant solo contributor who makes a clean, maintainable system, and documents it nicely, and politely and sensitively hands it off to more junior staff to maintain while he/she moves on to the next big thing -- and what a joy that is! But more often they're the brilliant asshole that you have to deal with, both their professional work and personal foibles.