I suggest the cause of inequality is the attention paid to the numbers and the yetzer horah to compare and contrast them. I look around, at my family both immediate and extended, the neighbors, the others davening in the shul where I go, and I could bet with certainty that there is a wide variety of incomes represented. Except that no one really cares, and it doesn’t really matter. The latter for multiple reasons.
Someone who is happy with his lot is far better off than someone with greater wealth but who is not happy with his. The tzuris that Klal Yisroel suffers, while sometimes a public or political issue, include many troubles that are experienced by individuals, not always known to others. So if someone has monetary wealth, but a family member who is seriously ill, does their income suggest they are happier?
Granted, someone on a meager salary might not be able to distribute tzedokoh in a manner that resembles the gvir. Is that all there is to our lives? The meager earner that gives according to his ability is doing his mitzvah royally, perhaps more or al least not less than the gvir who doles out the larger sums.
Lastly, מה ה’ שואל מעמך? I thought our existence as Am Yisroel is about what we are, not about what we have. Why are we paying attention to these differences as “inequality”?