KEY POINTS
  • Last year, customers in the U.S. returned about $351 billion worth of items that they had purchased from brick-and-mortar retailers and online stores, according to estimates by National Retail Federation.
  • Buyers return a huge number of packages they buy from Amazon and other e-commerce sites, so much so that retailers are sometimes left with little choice but to get rid of large swaths of inventory at a cost.
An employee walks between rows of storage racks at one of Amazon.com's fulfillment centers in Rugeley, U.K.

There's a good chance that the $100 printer, the $300 wide-screen monitor, or the $170 router you recently bought from Amazon weren't supplied to the e-commerce giant by their original manufacturers. In fact, the order may have been fulfilled by someone like Casey Parris, who resells items that customers previously returned to retailers.

Based in Florida, Parris spends about five hours each day visiting thrift stores and scanning auction and liquidation websites for interesting items, he told CNBC. Sometimes he finds auto parts, other times it's a pair of sneakers, and occasionally he purchases printer cartridges — all with the goal of reselling them.