If I may chime in. I'm strongly against an income cap.
I earn extraordinarily well - around a quarter million a year, with odds of doubling that a few years down the line.
Is that too much? Of course! There's no justification of why I'd earn multiples of nurses, policemen, or most other professions. There's no moral justification to my income.
But there is an economic one. Looking how I got to this point - I started working (in parallel to school of course) at 14, and never stopped til this day. I graduated in the top percentile from school, then same from undergrad, then same from postgrad. I invested all of my savings into my higher education and went to some of the most renowned universities there are, pouring in 100k or so for my degrees (not funded by family, but by my own work and strict saving). I now work 12 hour days, no breaks in between, barely any holidays, no public holidays.
And yes I know that sounds terribly arrogant, but I'm not saying this to boast. I'm extremely aware that in spite of all the effort, a very large part of where I am is purely down to luck as well.
But the gist is - reaching very high income often goes hand in hand with immense effort. And even then there's no guarantee - probably 9 out of 10 or so people I know with similar trajectories don't end up earning nearly as well.
But you need this carrot on a stick in order to get enough people to actually try. I would have NEVER more or less given up on my free time for more than a decade if the best I could have dreamt of was to earn twice the average or something like that.
Plus, keep in mind, even at such an income level I'd needs more than 10 years to pay off a 60 square meter flat where I live, but that's another story

generally though, I think it's almost impossible to get enough wealth purely by income that really causes significant sociaty issues. To address the real disparity of wealth, you'd need to address inheritance. Billionaires don't earn their money with income in the vast majority of cases. Ajd even if somebody did, with proper inheritance taxes, they wouldn't keep it for much more than 50 years or so before it goes back to society