For a country that trumpets the success of its economic system and the power of its local currency, it is very difficult as a foreigner in North Korea to buy anything with it.

At the Yanggakdo Hotel, one of a handful of places foreigners stay in Pyongyang, a can of peaches is listed at 130 North Korean won — $1.30 at the official rate of about 100 to the dollar. Yet staff won't accept payment in won, only taking dollars, yuan or euros. If they don't have proper change, they may give back a mix of currencies adding up to the amount owed.

That can of peaches highlights a contradiction at the heart of North Korea's command economy.