Like many big court cases, it began with a simple question: Are you paying more than you should? In the case of De Coster et al. v. Amazon.com, Inc., a federal court in Seattle has decided that the question should be put to a jury. The answer could affect about 288 million American customers.
A lawsuit was first filed on May 26, 2021, by a group of consumers led by Elizabeth De Coster. They say that Amazon used its huge market power to stop other online sellers from offering lower prices. Think of Walmart, eBay, and Target as examples of competing sites where the same item could have sold for less. Plaintiffs say that Amazon’s pricing policies kept prices artificially high across the entire e-commerce landscape, like an invisible ceiling pressing down from below.
The main issue is Amazon’s “price-parity” or “most-favored-nation” policy. Through Amazon’s Buy Box algorithm, product rankings, and visibility controls, this system made it less likely for third-party sellers to list their goods cheaper elsewhere. Amazon got rid of its clear price-parity clause in 2019 and replaced it with something it called a “Fair Pricing Policy.” This trial will basically decide if that change was real reform or just a way to get around the law.
Take a moment to look at the scale. Every U.S. customer who bought five or more new physical goods from third-party sellers on Amazon’s marketplace on or after May 26, 2017, was part of the class certification that Judge John H. Chun granted in August 2025. That’s a big group of shoppers who are upset. If you look at it another way, that’s the biggest group of consumers ever approved in an American antitrust case. The Ninth Circuit didn’t overturn the certification, so it stands before a trial that has been set for June 2027.
Amazon, for its part, says it hasn’t done anything wrong. Throughout, the company has said that its sellers set their own prices and that its rules are there to protect customers from fake goods and unfair business practices. It’s almost like the defense comes naturally—tech companies have been using it for a long time to say that platform rules help users instead of hurting competition. It’s still not clear if that argument will hold up in a federal trial, where economic experts, internal communications, and pricing data will all be taken into account.
In September 2023, the FTC and seventeen state attorneys general brought their own case against Amazon, which is related to this one. That case, which is also in the Western District of Washington, asks for structural remedies, which means the government doesn’t just want money for damages; it also wants Amazon to change how it works. The two cases together show that the company is under coordinated legal pressure from both private citizens and federal regulators at the same time. It doesn’t happen often. When it does, it usually means more than just a normal lawsuit.
The economic method at the heart of De Coster is what makes it so interesting, not just its size. A lot of the plaintiffs’ legal strategy is based on algorithmic analysis and econometric modeling, which is like using data science in court. The point of the argument isn’t that Amazon told sellers to raise prices in memos. It was because Amazon’s systems set up structural incentives that got the same result without leaving clear traces. It’s harder to make that case and harder to argue against it.
Most shoppers still don’t see how this lawsuit will affect them in real life. There isn’t a settlement to get. This year, there will be no check in the mail. If you bought five or more items from third-party Amazon sellers since 2017, you are probably already in the class. You don’t have to do anything to stay in, but you do have to opt out by August 31, 2026, if you ever want to sue Amazon on your own.
No matter what happens with this case—a landmark verdict or a quiet settlement reached before 2027—it has already done something. It has made people really think about how the world’s biggest online market sets the rules for doing business and whether those rules are fair.
