That's nonsense. The work of a financial executive might be quantified by how much money the company is making, but judging the output of a professor is completely subjective. Sure you can do some bean counting by looking at the number of publications and citations, but 10 years of work condensed in one paper may just be more of a contribution than 10 derivative papers, or not, it's difficult to tell without hindsight, and even then presumably lots of work is under-appreciated.

My conclusion is that we cannot with a straight face claim that we can justify such a pay gap in this case, so whether it is justified is the wrong question.

>how do we know it's not justified? Presumably the pay reflects the work done. Again, do you think studies haven't been done? That's the core of the discussion: pay does not reflect the work done, and it is sometimes even inverted.