That's true that we can distinguish capitalism from communism based on their respective mediums for power exchange.

So if we recognize money (or perhaps more specifically property) as the primary medium for exchanging and expressing power under capitalism, what would you say is the main medium for expressing power under communism? I think the theoretical answer might be "work", i.e. one's contribution to society, or else just a person's communally recognized "right" to power.

Although in practice, I think power under communism is actually represented largely by one's proximity to the people in charge - i.e. the people whose job it is to actually distribute resources to everyone. And so we again bump into the issue of power accumulating into a kind of pyramid scheme, similar to capitalism.

I know you're not arguing in favor of communism specifically. But I think my main point is that money as a medium for power doesn't really cause, or even necessarily exacerbate, the effects of greed, relative to other power mediums. At least as far as I can tell.

Obviously, the world's power structure is totally out of wack right now. And I'm not exactly sure on the way forward. But I think greed is a given, and we really just have to find ways to use it, rather than demonize it. And I think whatever we come up with, the main challenge is just in making sure that the peaks and troughs of power tend not to be so different - more like waves or sand dunes, rather than like mountains.

As a final side note, a nice thing about money-as-power that people don't talk about much is that it's actually, I think, more democratic than systems where the government itself is the only means to power. Money acts as kind of a back door, or black market, to power, relative to the government's physical power, and those two power systems (money and the government) kind of keep each other in check, in a way.