[exelius]

It depends on whether their currency is inflated or deflated relative to its market value. In a case like China, their currency is artificially deflated, so they will happily trade dollars for yuan all day long (but not the other way around). In a case like Argentina or Zimbabwe, the official exchange rate is something like 10 to $1, but the man on the street will give you 50 to $1.

Basically, with restricted currencies, you can often trade easily one way but not necessarily the other. The idea behind this is to make it easy to bring your money into the country on favorable terms, but hard to take it out (so you have to spend it there and repatriate the money through transfer of goods). In an inflationary system, you often have a capital class in power in a country, and high inflation keeps them in power since they own all the means of production. Unfavorable exchange rates and high prices discourage foreign investment, which can be desirable in corrupt or autocratic regimes. More often than not though, long-term high inflation is unintentional and a sign of bad monetary policy.