Capitalist economies are not sustainable. That's kind of their point: Line goes up, even though resources are finite (which economists conveniently ignore). Hence, they can't be sustained ad infinitum. We're all borrowing/stealing from somewhere, including from nature. (And the harder we believe in capitalism, the faster humanity will crash because resources are getting used up.)
Ultimately, money is a means to an end anyway: Making sure society functions well enough that everyone has food and shelter. Other than that, it's just imaginary figures.