I'm always interested in this idea when it comes up because I don't understand what people think the billionaires are hoarding. For curiosity's sake could you give me a quick enumeration of the physical, real-world resources that you think the billionaires are using up? Like, do you think they have 10 million in rice hidden in a silo for a rainy day?
And billionaires do effectively hoard things like rice. That's what the futures market they invest in is all about.
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.
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.