No need to take his word for it. If you look at the Austrian school theories you'll see that those things aren't accounted for. Another crucial element that isn't considered is velocity of money, and the concomitant effects on money supply. The Austrian school has a lot of important insights, but it omits several important factors. It has a good and useful set of ideas, but it's not the grand unified theory of economics that many libertarians (like me) wish it were.