Shoppers can bid for discounted gift cards at auction sites like eBay.com. The actual discount depends on the bid price, but several cards can be purchased for less than face value.

However, consumers will have to do due diligence to make sure they get a true deal, says Testa. To avoid scams or misunderstandings, Testa recommends that buyers ask potential sellers what the expiration dates are on the cards offered, and if there are any other penalties or restrictions.

For example, some retail gift cards might be good for in-store use only, but not online shopping. Buyers have to be cautious they're not purchasing a gift card in which the face value is misrepresented, Testa warns.

Consumers should also ask if there are any additional service fees involved, and they should evaluate the seller's reputation. "Always check the seller's previous feedback before bidding on a gift card," says Testa.

This may seem like a lot of work upfront, but it's important to verify as much information as possible when dealing with individual sellers. "If you're looking at a secondary market, the consumer may not have as much protection," says Testa.