I don't know anything internal about Valve, and I'm sure their system isn't working perfectly, but I'd imagine that the people generating 10-100x salary are get

I don't know anything internal about Valve, and I'm sure their system isn't working perfectly, but I'd imagine that the people generating 10-100x salary are getting bonuses that they're happy with, at least in most cases. That would be the more rare case of an employee getting screwed (delivering massive value, underpaid). Much more common is an employee who's screwed by being given inappropriate work, few or no opportunities to advance, but then compensated accurately (this might mean getting laid off) for the value delivered (with no allowance made for the error being in that person's work allocation). No evaluation process is perfect, but a system where being unlucky means you live on your salary for a year is better than one where being unlucky fucks up your career, possibly beyond that job if you get fired abruptly with no severance. Microsoft-style stack-ranking is the latter.