The price differential between the U.S. and China opens the door to a lively grey market.
FORTUNE -- Four days after Apple (AAPL) began taking pre-orders for the new iPhone 5C, the device is available in all colors and configurations except for the most expensive: the T-Mobile and SIM-free models that start at $549.
Why would that be?
It's simple, really. A lot of those unlocked phones are headed for overseas grey markets.
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