A shopper in a 2024 federal lawsuit bought a CD on Amazon for $29.43. At the exact moment of purchase, a different seller was listing the same disc on the same page for $18.88. The cheaper option existed. It just wasn't the one Amazon put in front of her (Hagens Berman, August 2024). That $10.55 gap wasn't an accident. It was the Buy Box doing exactly what it was designed to do.
What the Buy Box Actually Is
On any Amazon product page, the prominent "Add to Cart" and "Buy Now" buttons belong to a single seller: the Buy Box winner. Every other seller offering the same item gets buried under a small "See all buying options" link that most shoppers never click. The stakes are enormous. Over 83% of Amazon sales flow through the Buy Box, representing more than $476 billion in transactions in 2023 alone (Repricer.com, 2025). Some estimates in ongoing litigation put that figure even higher, at 98% of all Amazon sales.
For sellers, losing the Buy Box is effectively losing visibility. For shoppers, whoever holds the Buy Box is the price you see, the seller you trust by default, and the purchase you make without thinking twice.
How Amazon Decides Who Wins
Amazon has never published a complete algorithm. What it has confirmed, and what years of seller experimentation have mapped out, is a rough set of factors:
- Fulfillment method. Sellers using Fulfillment by Amazon (FBA) have a structural advantage over those shipping independently. Amazon controls the logistics, the Prime badge appears automatically, and the algorithm treats FBA delivery estimates as more reliable.
- Price competitiveness. The algorithm checks whether the total landed price (item plus shipping) is competitive — but "competitive" is measured against Amazon's own preferred range, not a true market lowest.
- Seller metrics. Order defect rate, cancellation rate, late shipment rate, and customer feedback scores all feed in. New sellers rarely win the Buy Box regardless of price.
- Inventory availability. A seller who frequently runs out of stock gets penalized in the rotation.
Notice what's absent from that list: whether the seller is actually offering the best price to the consumer.
The FBA Fee Problem Hidden in Your Purchase Price
When a third-party seller uses FBA, Amazon charges fulfillment fees, referral fees, and often advertising costs. According to data from Marketplace Pulse, Amazon now takes roughly 50 cents of every dollar a third-party seller earns on the platform, once FBA fees, referral fees, and advertising are combined (TheStreet, citing Marketplace Pulse, February 2024). FBA fees alone run between 20% and 35% of the item price.
Those costs don't disappear. They get baked into the price you pay. A seller shipping independently, without FBA, can sometimes offer the same item cheaper precisely because they're not absorbing Amazon's logistics markup. But that seller almost never holds the Buy Box. So you don't see them.
Buy Box Rotation and the Illusion of a Stable Price
When multiple sellers are close in their metrics, Amazon "rotates" the Buy Box between them. You might load a product page at 10 a.m. and see Seller A at $34.99. Reload the same page at 2 p.m. and Seller B has it at $37.50. Both are "winning" the Buy Box during their allocated share of impressions. The price you pay depends on when you happen to visit — not on any deliberate choice you made.
This rotation also means that the price shown in your browser history, in a price-tracking graph, or in a screenshot from a friend may not be the price you'll see when you arrive. It makes comparison shopping harder than it should be.
Amazon Uses the Buy Box to Control Prices It Never Sells Itself
The most significant thing regulators have started examining isn't just who wins the Buy Box — it's how Amazon uses Buy Box suppression as a pricing lever over sellers it doesn't employ.
In April 2025, Amazon penalized sellers who raised prices to offset new tariff costs by stripping their Buy Box placement. Sellers reported being effectively shut out of visibility until they reduced prices back down — even though Amazon wasn't the one selling the product (Fortune, April 2025). The threat of Buy Box removal functions as price enforcement without a written contract.
Germany's Federal Cartel Office formalized this concern in a landmark ruling on February 5, 2026. The Bundeskartellamt prohibited Amazon from using price control mechanisms that remove listings or exclude them from the Buy Box when a seller's price is deemed "too high." For the first time in its history, the agency exercised its "profit skimming" power and ordered Amazon to disgorge approximately €59 million in economic benefits gained through this conduct (A&O Shearman, February 2026). Amazon has said it will challenge the ruling.
The context matters: Amazon's German marketplace accounts for roughly 60% of all online retail sales in Germany (A&O Shearman, February 2026). A platform with that kind of market share setting invisible price floors across every seller on it has consequences that reach every consumer who shops there.
When the Buy Box Winner Is Not Your Best Option
There are specific situations where the Buy Box default is reliably worth questioning:
- Books, music, and media. Third-party sellers frequently list the same editions at 30-60% below the Buy Box price, often with Prime-eligible shipping. This category is where the Hagens Berman lawsuit examples came from.
- Older or non-trending products. Items that were popular two years ago often have sellers competing on price, but the Buy Box winner may still be holding a premium from when demand was higher.
- Products with many fulfilled-by-seller listings. Categories like tools, housewares, and some electronics attract independent sellers who absorb lower margins but pass savings to buyers — if you look for them.
- Amazon's own retail listing vs. third-party. Counterintuitively, Amazon's first-party price is sometimes higher than a third-party seller's FBA listing. The algorithm favors Amazon's retail offer even when it's not the cheapest.
How to Actually Compare All Sellers
The "See all buying options" link, small and easy to miss below the Buy Box, opens a full list of sellers with their prices, conditions, and shipping estimates. Clicking it takes about three seconds. Most shoppers never do it. Here's a practical approach:
- Click "See all buying options" and sort by price. Look at the total price including shipping, not just the item price.
- Check the seller's feedback score and number of ratings. Anything below 95% positive with fewer than 500 ratings deserves scrutiny.
- For new items, confirm the seller is listing condition as "New" — not "Like New" or "Renewed." These are often mixed into the same listing pool.
- Verify delivery estimates match your needs. Some cheaper sellers have slower shipping that isn't surfaced prominently.
- If you find a significantly cheaper seller, check whether the savings outweigh any return policy differences. FBA sellers follow Amazon's return policy; fulfilled-by-seller listings may not.
BuyWise recently analyzed a home goods listing where the Buy Box price sat 22% above the cheapest eligible third-party seller offering the same item, new, with Prime-eligible delivery. The gap only appeared after clicking through to all sellers — the Buy Box price was the only one visible on the default product page.
Across 50 recent BuyWise product analyses, 38% flagged listings where review patterns suggested artificially inflated ratings — a reminder that even after you find a cheaper seller, the product itself may need scrutiny before you commit.
What This Means for You
The Buy Box is a convenience feature that has accumulated more power than most shoppers realize. It concentrates the visibility of an entire product's seller ecosystem into a single button — and the selection criteria behind that button prioritize Amazon's business interests alongside, and sometimes ahead of, yours.
That doesn't mean the Buy Box winner is always the wrong choice. For many everyday purchases, the default seller offers fair pricing, reliable fulfillment, and a smooth return process. The problem is assuming that's always true without checking.
Three habits close most of the gap: click "See all buying options" on anything over $20, factor in total price not just item price, and treat the default offer as a starting point rather than a conclusion. The $10 savings on a single CD purchase described in the federal lawsuit isn't a fluke. It's a repeatable pattern for shoppers who know where to look.
