If a company answers this way, it is likely that you would succeed on a claim under the California Equal Pay Act. This kind of hair splitting doesn't generally go over well.

>The California Equal Pay Act

Does this account for the vastly different levels of output from employees? I would have to imagine nobody believes quality of work and productivity are actually equal amongst coworkers.

Pay is more a measure of what the worker is willing to accept than a measure of quality or productivity.

If you're paying someone 3x someone else, they're probably doing different jobs, which should have different pay ranges. A range of 20%, or even 50% is probably acceptable for salary (also of note the CA and CO laws only require salary disclosure, performance based bonuses or equity award ranges don't need to be shared) based on performance in a role. A difference of 3x or 10x (or 50x as is the case above) in salary means that the expectations are different.

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.