Fiat currency is like... tulips
You can print it at will, same way you can cultivate tulips. You can have as much tulips and fiat as you want, the limit is the sky... or hyperinflation.
If you can manipulate the amount of fiat/tulips then you can manipulate the price.
Transactions are not backed by an open system in neither of them.
Pics Sources:
http://www.countryliving.com/gardening/a35956/tulip-fun-facts/