There's one question, regardless of if you believe this is "fair" or not, around whether structural inequality at this level is harmful to society regardless of fairness. I tend to believe it is, based on historical precedent of what happens in highly unequal societies (it tends to not be good), but that's a separate question from the one about fairness.
To analyze whether this is "fair" or not, I think the best perspective there is Rawls's framework, which is the maxi-min idea. To summarize, the idea is that inequality is okay to the extent that it improves the minimum position. For example, if you start out with some totalitarian society where everyone makes $25k, it's okay for someone to start making $200k so long as it doesn't mean that someone else now makes less than $25k. Economically, that comes out as something like: it's okay for the top end of the wage spectrum to increase because they're producing more value and capturing that value for themselves. It's not okay for them to increase because they're capturing value that other people are creating instead. If someone making $500k starts making $1MM because they're producing $500k more in value, that's acceptable. If they do that and they're only producing $300k more in value, and the other $200k increase is coming from other people's productivity increases, then that's not "fair" and shouldn't be acceptable.
So, which one is it? Does anyone have a compelling argument? In the financial sector, for example, I think it's pretty easy to argue that it's the latter: people who privatize gains and socialize losses are enriching themselves far out of proportion to the value they create. When it comes to startups and new businesses, it often works the other way, in that the person starting the business, even if they become hugely wealthy, does so by creating even more value than they capture. I'm not sure it's obvious if what's been going on for the last 40 years is one way or another.