Yeah, that's what I don't get either.  How does he get it for "free"?  If that's one of the uses to which money can be put, doesn't that make money more valuable? And wouldn't that value have been factored into the exchange in which the "money hoarder" originally acquired the money by trading goods and/or services for it?  And isn't hoarding money also not free in the opportunity cost sense? If you're hoarding money, that means you're foregoing current consumption and the opportunity to invest that money for a greater return.

And even if it were "free," I still don't get how you're imposing a cost on society.  Again, it seems like the effect of hoarding your money is to make goods and services cheaper for everyone else (because there's now less money chasing the same goods). That seems like a benefit to society rather than a negative externality. And that's why it's rewarded with increased purchasing power in an economy that uses sound money.