I tend to believe that the throughput of the top 5-10% can be exponentially more than the next 5-10%. The objective for a lot of these firms is to get the top couple percent and get 4x as much value of out someone but paying 2x as much. As it relates to the parent comment, I think there is an incredibly high demand for the top 5-10% of tech talent and exponentially less demand for the subsequent talent. It's very similar in NYC for finance talent. I know people who work in SF and NYC both who work insane hours but they get paid SO MUCH MORE for it.
So, no one is scrambling for good engineers or good bankers or good consultants but they are scrambling for that tiny sliver of the market that they believe will generate exponential returns and turn into leaders of the company.
Perhaps this is simply too anecdotal and I've had a poor experiences, but I can say, in my personal experiences, most candidates we've talked with are doing 1x and there are other candidates doing 2x, 3x, or better. Perhaps not 10x, but I have definitely seen very similar people on paper deliver on VERY different levels.