This is almost a natural law of wealth. When you have significant capital, you can do things like loan it out with interest, leverage it into getting loans to build more capital, etc. If one assumes that the wealthy are using their money to buy commodities and selling those commodities with the expectation of getting their initial money back plus some delta, then it becomes fairly trivial to demonstrate that the more…
What's interesting is that while intuitively this makes sense (for the reasons you gave), the implication (that the rich get richer and inequality grows) is the opposite of what was hypothized by Kuznets (https://en.wikipedia.org/wiki/Kuznets_curve); the latter hypothesis, to my limited understanding (as a non-economist), is fairly mainstream, and has influenced plenty of politics and public policy.