As the head of a company that sells used consumer electronics, David Chen follows sales of the iPhone with the precision of a mathematician. At the outset, the price of the first version of Apple’s music-playing wireless device behaved as expected: When the newer iPhone 3G hit store shelves, demand for the earlier iteration plummeted. Then the unexpected happened. Within days of the iPhone 3G launch, demand for used, older iPhone models began rising, and prices began a steady climb. “We’ve been raising our prices over the past few weeks,” says Chen, who runs NextWorth.com.
