Using athletics as an example, it's quite common to see the best players making $30+ million/year while their peers doing the same job (albeit not nearly as well) are getting paid half a million.

The peer pay differences are less pronounced in other fields, but why would we assume people are "essentially the same" at their output? I have definitely seen full stack developers that are "doing the same job" 3x-5x better than some of their peers in many cases, when you compound quality and efficiency. Not every company has enough people for tiered job rating buckets like Google, Amazon etc.