The thing is the real exchange price of something is determined by the market and in a world where you can buy nearly anything with usd and almost nothing with iranian money its clear, that the USA can controll the exchange rate of their currency and so they can feign a demand thats actually not there and because every trade in the real world is based on us dollar the supply can almost never exceed the demand... and thats the whole trick so they can print more and more dollars as they go..