My take on this is that once you have machine of infinite stuff creation, just like all your other peers - how do you compete? What is the status?
I believe the rich, just like many not as rich (who probably has it to the lower degree), have the need for social status. Right now status is equated to money - the higher your valuation, the higher status. If money is nothing, and you can acquire anything you want (this is too strong of a claim as well) - what is the thing that defines your status? One of the solutions - the happiness of your "Kingdom". There might be others. But money is not only for exchange nowadays, it's a status as well.
I believe the rich, just like many not as rich (who probably has it to the lower degree), have the need for social status. Right now status is equated to money - the higher your valuation, the higher status. If money is nothing, and you can acquire anything you want (this is too strong of a claim as well) - what is the thing that defines your status? One of the solutions - the happiness of your "Kingdom". There might be others. But money is not only for exchange nowadays, it's a status as well.