[Teutonics]

If I had to guess, there is probably some type of "incentive" attached to the cards for the retailer, which drives the price higher than face value.

I know this is the case with baby formula "checks", which also sell for more than face value on ebay. What happens is grocers (e.g. small non-corporate convenience stores) buy the checks at a price higher than face value, but lower than what they receive from the manufacturer, and submit them for refund. It's free money for them...