It is not stuck. The billionaires are not hoarding all the dollars. They have stock in their companies, which is worth varying amounts of dollars. Them owning stock does not deprive you of any dollars.
There's "rich people" buying houses, which are investment funds that buy property to rent - that is still availalbe on the market and isn't decreasing the supply of housing.
Rich people buying homes for personal use can't have an appreciable effect on pricing. You couldn't afford a billionaire's eighth home in whatever city even if it were available for sale anyway.