First-order effects

• Professional sellers crossing $1M are now large enough businesses that Amazon's subscription-plus-fee model captures them twice — recurring revenue from the account itself and a growing percentage of every sale.
• Amazon gains its most valuable merchant tier precisely where its fee leverage is strongest, since high-volume sellers have the most to lose from losing Buy Box placement or account standing.

Second-order effects

• As more sellers reach this scale, Amazon can keep raising its take rate — the trajectory documented from 30% of each sale in 2019 toward 34% and beyond — because seven-figure sellers have sunk fulfillment and logistics investment into the platform and face high switching costs.
• Rivals' marketplaces must compete for these proven mid-market sellers on fee structure rather than reach alone, since the successful sellers are the ones whose volume funds both sides' unit economics.

Third-order effects

• If the pattern holds, Amazon's marketplace structurally bifurcates into a small cohort of million-dollar sellers who anchor its fee revenue and a long tail of new entrants feeding the funnel — making Amazon less a retailer than a toll-taking access layer between those sellers and shoppers.
• That concentration invites regulatory attention on whether platform fees and first-party competition leave scaled sellers genuine alternatives, a scrutiny thread visible in later coverage of Amazon's own-brand practices.