I don't think they think that no one will pay. I think they don't think about it at all, or they think that government somehow has unlimited resources at its disposal.
It's actually that "billionaires" will somehow produce a whole lot more things and pay for it all for everybody else, absolving themselves of any further rational thought or moral responsibility to those with less than themselves.
https://www.youtube.com/watch?v=ee8GedvPmBU