here's your espresso sir, that will be $3.95 please
sure no problem! i'll just pay for it with this big shiny gold bar, thanks!
um sir, we don't accept payment in big shiny gold bars
why not? can't you just mint it down into smaller denominations and give me the change?
unfortunately we don't have a coin minting press in this coffee shop, sir.
but... wait... they told me gold is real money!!!