Amazon Is Bigger Than Ever. So Why Are Fewer Sellers Joining?

Amazon’s marketplace is getting bigger. It is also getting harder to join. These two facts seem like they should contradict each other, but they don’t. They explain each other.

In 2025, Amazon and its sellers moved roughly $830 billion worth of goods worldwide. Independent sellers accounted for about $575 billion of that, which means third-party merchants now drive close to 70% of Amazon’s total commerce. The platform has effectively tripled in size in under a decade. This is not a shrinking opportunity. This is one of the largest commercial ecosystems ever assembled.

And yet new sellers are showing up in record low numbers.

Only about 165,000 new U.S. sellers registered last year, the weakest intake in roughly a decade. At the same time, the revenue already inside the system is concentrating at a remarkable pace. Fewer than 8,000 sellers now generate half of U.S. third-party marketplace sales. That is about 1.6% of the active base controlling 50% of the pie. Three years ago, it took nearly twice as many sellers to hold that position.

The upper end of the seller economy is thriving. Over 100,000 sellers now generate at least $1 million a year, far more than a few years ago. The number of nine-figure sellers has multiplied. The big are not squeezing the small out of existence so much as they are absorbing the growth. The platform keeps expanding, but the expansion accrues disproportionately to the operators already equipped to handle it.

What changed is not consumer demand. What changed is the cost of being visible. Amazon’s advertising business now generates more than $68 billion annually, which quietly makes it one of the largest ad platforms on the planet. The marketplace still rewards good products, but it rewards them through a financial system that looks increasingly like media buying combined with logistics arbitrage.

Meanwhile, competition has industrialized. A large share of sellers now operate directly from manufacturing hubs in China, collapsing supply chains that used to include multiple intermediaries. Domestic sellers respond by scaling operations and hiring professional teams. The middle ground, the casual operator experimenting with a clever niche, has become fragile.

Amazon itself has evolved to match this environment. The company extracts value from facilitating commerce more than from owning inventory. Third-party sellers account for the majority of GMV but a smaller share of unit volume, suggesting that Amazon prefers to anchor everyday essentials itself while letting merchants compete in higher-value categories. It is a neat balance: Amazon keeps traffic through price leadership, sellers drive revenue through specialization, and the company collects fees from both sides.

The result is a marketplace that behaves less like an entrepreneurial frontier and more like a capital market. Entry still exists, but the cost of entry is legible. Fewer people attempt it casually because the system makes clear what participation requires. Longevity compounds. Incumbents scale. Newcomers face an environment that rewards operational discipline over improvisation.

This is not the death of the Amazon seller. It is the professionalization of the Amazon seller. The opportunity did not disappear. It got institutional.

And institutional systems tend to concentrate power, not because they are unfair, but because they reward whoever can operate them most efficiently. Amazon is now large enough that it behaves like infra. The scrappy seller did not vanish. The infrastructure simply grew around them.

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