If they invest it or hell, even put it in a savings account, the money is having a positive impact on the economy. If they buy a ridiculous $50M yacht? That money flows to the company that built it.
Here's an analysis showing that capital is earning more than labor mostly due to housing prices:
http://www.brookings.edu/about/projects/bpea/papers/2015/lan...
When you have a millionaire who is "rich" because they own their house (no mortgage) and the house is worth more than a million dollars, they might still be living paycheck to paycheck. The difference being they could leverage their house if they needed money on short notice.
That said, it would be interesting to see what shooting down rent-seeking taxes would do here. If for example you allowed copyrights to expire in a reasonable time, then you could have people put on a play and keep the profits. Something they can't do today.
Why all the downvotes? HN'ers like yachts and empty mansions, huh?