What exactly is the "fair share" of someone's income that he’s earned that he should be able to keep?

90%

Jeff Bezos reportedly scooped up a $79 million mansion in Florida’s exclusive “Billionaire Bunker” island — two months after buying the home next door for $68 million.

https://nypost.com/2023/10/13/jeff-bezos-buys-billionaire-bunker-florida-mansion-for-79m/

Mark Zuckerberg’s $46.5 billion loss on the "Metaverse" since 2019 is so huge it would be a Fortune 100 company...but his net worth is up even more than that. Don't tell me the super-rich can't afford a wealth tax.

Now, please tell me why their effective tax rate should be lower than my 24%.

I don't know. As much as they can spend wisely? For billionaires, that's 0%, of course.