Land. Billionaires own thousands of empty luxury apartments in city centres, while the poor people who clean them travel in from the outskirts.

And billionaires do effectively hoard things like rice. That's what the futures market they invest in is all about.

I don't disagree, but "the poor people who clean them" are doing that because it pays better than they could get elsewhere, otherwise they wouldn't do it (assuming no coercion on the billionaire's part, which would be illegal).

If the billionaires magically ceased to exist and poor people owned the apartments, I don't think they'd be paying the other poor people as much to come clean them.

Also labor. If a billionaire buys a luxury product like a jet, or a yacht, or even just an expensive car, all the labor that goes into production and upkeep of that product is used up solely for the benefit of the billionaire. If wealth was distributed more fairly, all that labor would go into things that benefit a wider audience.

I think easiest way to understand it that they hoard access to capital. They suck it out of consumers in the economy, denying smaller entrepreneurs access to it.

People won't buy your SaS for $4.99 a month so you can earn your first million if they spent all of their money on iPhone priced higher than it needs to be.

Strongest benefit of the market is competition that allows million ideas to be tried to find the thousand that will benefit the society. One person with billions of dollars won't have million ideas, let alone thousand beneficial ones.

They also hoard other stuff like land and real estate but that's just means to an end. Extracting capital, denying it to everybody and keeping it all under singular command.