Amazon is asking some FBA sellers to submit per-unit bids to get their products into Sub Same Day delivery, the tier that reaches customers in as little as two hours across 2,300 metro areas. The invitation went out by email earlier in August, and the pitch is straightforward: Amazon says products in the Sub Same Day network have seen 12% higher sales on average than the same products shipping through standard FBA.

The mechanism is what makes this different from a standard fee increase. Sellers aren't paying a published rate. They're bidding against each other.

How the Bidding Works

Amazon's email language is specific: “You pay only for units that actually ship through Sub Same Day, at the per-unit price you bid. Participation is optional, and you're never charged more than the price per unit you set.”

Amazon evaluates bids using factors including customer feedback, so price isn't the only input. An Amazon spokesperson framed it as expanded seller control: “For the first time, sellers can choose which additional products to offer at faster speeds based on their own business expertise and customer insights.” The spokesperson added that Amazon “will continue to place a wide variety of products from independent sellers throughout our Same Day network at no additional cost to sellers.”

The scarcity driving this is real. Amazon's Sub Same Day facilities stock roughly 100,000 products, a fraction of the millions carried across traditional fulfillment centers. There isn't room for everyone, which is precisely why an auction exists.

Why Sellers Are Uneasy About the Structure

One seller who shared the invitation on social media put the objection plainly: Amazon already charges customers for ultra-fast delivery even when they hold Prime membership, and now it's asking sellers to contribute as well.

Scott Needham, who has sold on Amazon for 13 years and runs market intelligence firm SmartScout, said FBA remains a good deal for fast shipping even with this change, but objected to the format rather than the cost. He'd prefer Amazon simply set an elevated flat rate for Sub Same Day and invite sellers to opt in. That way, he said, “there's no game theory.”

That's the real complexity here. A published fee is something you can model. A bid requires guessing what competitors will pay for the same limited shelf space, and getting it wrong means either overpaying or losing placement entirely.

The Hidden Cost Beyond the Bid

Vanessa Hung, CEO of Online Seller Solutions, pointed to an inventory cost that arrives whether or not you bid. Faster delivery windows require inventory positioned closer to customers, which means buying more stock and spreading it across more facilities.

“Before, the same warehouse could serve Raleigh and Charlotte,” Hung said. “Now, you need to have inventory in Raleigh and in Charlotte in order to have the 30-minute delivery window.”

She also flagged the ranking consequence, which is the part that turns an optional program into competitive pressure: “Amazon will prioritize in search results, or even in Alexa results, whatever gets there faster. If you want to keep playing at the highest level, you need to bid for that and pay more.”

Her summary of the whole thing was blunter: “I roll my eyes, and I'm like, okay, this is another fee.”

Where This Fits in a Year of Rising Costs

This lands on top of an already expensive year. Amazon's January fee restructure introduced three price tiers, raised placement fees by as much as 179% for some size categories, and removed the Ships In Own Product Packaging discount for bulky items. Holiday peak fulfillment fees started October 15. New commercial liability insurance requirements hit November 2.

In April, some sellers staged a one-day Amazon ads boycott after the company began deducting ad costs directly from sales proceeds rather than allowing credit card payment. Hung noted that some sellers are actively shifting volume toward TikTok Shop, where selling costs are lower.

What to Do If You Get the Invitation

Run the math before bidding anything. Amazon's 12% sales lift figure is an average across the program, not a guarantee for your category or your ASINs, and your bid comes out of margin on every unit that ships through the tier.

The question worth answering first: does 12% incremental volume at your specific margin cover the per-unit bid you'd need to win placement? For thin-margin products, the answer is likely no. For higher-margin items in competitive categories where delivery speed influences the Featured Offer, it may be worth testing on a narrow set of ASINs rather than your full catalog.

Participation is genuinely optional, and Amazon says non-bidding sellers still get Same Day placement at no cost. The pressure comes from ranking, not from the fee itself. If competitors in your category bid and you don't, the speed gap eventually shows up in placement.