Third-party sellers were reshipping Walmart bargains to Amazon buyers at a markup

San Francisco resident Catherine Lelong ordered detergent on Amazon and received a Sam's Club box. She hadn't ordered from Sam's Club: an Amazon seller had bought the detergent on Samsclub.com for one price and sold it to her on Amazon for several dollars more, having it shipped directly from Sam's Club to her home. Another resident, Ariel Bryant, got paper towels in a Walmart box — paying double Walmart's price.

The practice is retail arbitrage: buying a product at one retailer and reselling it on another shopping site for a profit. It isn't new, but it grew as Amazon onboarded more individual sellers and software tools automated the activity — by 2016, 47% of items sold on Amazon were sold by someone other than Amazon, a share rising every quarter.

For Amazon the marketplace boom was mostly good: it expanded selection without inventory risk and took a cut of every sale. But arbitrage sales came at the expense of customer trust — the asset that made them possible. 'I feel a bit cheated, which I don't love,' Lelong said. Bryant stopped assuming Amazon's prices were competitive: 'I wonder if they were doing the same thing.'

An Amazon spokesman pointed to the seller policy prohibiting buying from another online retailer and shipping directly to customers, with suspension or revocation of selling privileges as the penalty. The seller behind Lelong's box, 'Order Me', claimed ignorance: 'We utilize the services of more than 20 warehouses throughout the country and they decide from where the item will ship.'

The trust halo is the margin: buyers assume Amazon has the best price, so a seller can buy at Walmart's shelf price, ship direct, and quietly keep the difference.

It turns Amazon's own price-comparison trust into the seller's profit margin: the buyer assumes the lowest price and skips checking.

Dropshipping from the other retailer means zero inventory risk and zero logistics — the Walmart box arriving is the only trace.

The mechanism scales with software, riding the marketplace growth that Amazon itself was cultivating.

It exposes the enforcement gap: a written policy with suspension penalties, against sellers who simply deny the practice.

Any marketplace that aggregates sellers inherits their arbitrage: a platform's price-trust is an asset third parties can monetise, and published rules alone won't stop it.

Affected customers said the discovery eroded their trust — Lelong now keeps her 'eyes more open' and feels Amazon is 'becoming a bit like an eBay'; Amazon kept the policy on the books while the marketplace share of its sales kept climbing.