I think the answer to your question depends on what you mean by a “completely egalitarian world”. Depending on the answer, I would ask: why does the kid desire to charge people to earn money in a society like that in the first place?

But yes, I think a lot of people would say there should be a cap on how much more wealth someone has compared to the median, for many reasons, such as the amount of political power it would yield him. The thought experiment uses a harmless activity for earning the wealth, but criticism of wealth inequality is often based on what happens _after_ the wealth is earned too. If in this example you will claim the world remains perfectly (socially) egalitarian and the kid will be benevolent, then maybe we can let him keep his wealth in the thought experiment. But that’s not the world we live in, and possibly never will be.

and you answer is...? There is an interesting article about inequality and intentions behind it: https://www.overcomingbias.com/p/inequality-is-about-grabbin... ... what do you think about it?

I have an interesting thought experiment too. First everyone has the same wealth and earns the same income. But there's a kid who strings razor wire across a road and starts charging 5c to unhook it while you pass by. Nobody is required to pay the kid, everyone does so entirely of their own free will. Things progress, and the kid now has 100x the wealth of anybody else. I ask the question: is this something that a good society would try to stop?

Which one is the better allegory of modern capitalism?

Now switch the paying 5c to buying endorsed sweatshop Nikes and owning hundreds of minimum wage paying franchises. Because that seems to be what the successful sports folks do.