Cost per Unit at Warehouse Scale: The Economics of Fulfillment

The Warehouse Economics Question

Every package that leaves a fulfillment center costs money to pick, pack, and ship, and the entire economics of running an ecommerce operation at Amazon's scale comes down to a version of the same question every warehouse operator has always asked, how do you get the cost of handling one unit down as volume goes up. Amazon does not publicly disclose an exact cost per package, but its aggregate fulfillment and shipping expense lines, reported every year in its 10-K filing, are large enough and specific enough to reconstruct the shape of the economics, and they show a business that has been getting modestly more efficient even as its absolute spending keeps climbing.

What Fulfillment Cost Actually Includes

Amazon's income statement breaks out fulfillment as its own operating expense line, separate from cost of sales, and it captures the cost of operating and staffing fulfillment centers and customer service centers, receiving, inspecting, and warehousing inventory, picking, packing, and preparing orders for shipment, and processing customer returns. Shipping cost is reported as a related but distinct figure, the net cost of shipping products to customers, which includes payments to third party carriers and, increasingly, the cost of Amazon's own delivery network, offset by any shipping fees the company collects directly from customers. Together these two categories represent the largest single operating cost bucket in Amazon's retail business, larger than marketing, larger than technology and content spending, and roughly on par with cost of sales as a share of the company's total expense base.

Amazon's Fulfillment Cost, By the Numbers

For full year 2025, Amazon reported fulfillment operating expense of 109.1 billion dollars, up from 98.5 billion dollars in 2024, an increase of about 11 percent. Net shipping costs came in at 102.7 billion dollars in 2025, up from 95.8 billion dollars in 2024, an increase of about 7 percent. Full year 2025 net sales reached 716.9 billion dollars, up 12 percent from 638.0 billion dollars in 2024. Put fulfillment expense over net sales and the ratio actually improved slightly, from about 15.4 percent of net sales in 2024 to about 15.2 percent in 2025, meaning fulfillment costs grew a bit slower than the overall business did. That is a meaningful signal on its own, since a company processing meaningfully more orders while spending a slightly smaller share of each sales dollar on fulfillment is, in aggregate, getting more efficient at the exact activity, moving physical goods, that has historically been the hardest and most capital intensive part of Amazon's retail business.

All figures are drawn from Amazon's fiscal year 2025 Form 10-K, covering the twelve months ended December 31, 2025.

Why Cost per Unit Falls With Scale, an Illustrative Model

Amazon does not disclose a precise cost per package, so the following is an illustrative model, not an official Amazon figure, meant to show the mechanics of why cost per unit tends to fall as fulfillment volume rises, a dynamic economists call economies of scale. A fulfillment center has a mix of fixed costs, the lease or ownership cost of the building, the base staffing needed to keep it running at all, the conveyor and sortation equipment installed, and variable costs, the additional labor hours and packaging materials needed for each additional unit picked and shipped. Imagine a mid sized fulfillment center with 40 million dollars a year of fixed operating cost and a variable cost of 3.50 dollars per unit shipped. At 10 million units a year, the fixed cost alone adds 4.00 dollars to each unit's effective cost, for a total cost per unit of 7.50 dollars. At 20 million units a year, the same 40 million dollars of fixed cost spreads across twice as many units, adding only 2.00 dollars per unit, for a total cost per unit of 5.50 dollars, a meaningful improvement purely from higher throughput, with no change in how efficiently any individual worker is picking or packing.

The Physical Levers, Density, Automation, Last Mile

Beyond raw volume, three physical levers determine whether a fulfillment network actually captures those scale benefits. Density, how tightly packed a fulfillment center's inventory and delivery routes are, since a facility serving a dense metro area can achieve far lower per unit delivery cost than one serving sparse rural addresses, which is exactly why the last mile, the final leg of delivery from a local facility to a customer's door, is consistently the single most expensive segment of the entire shipping journey on a per package basis, more expensive than the long haul transportation moving goods between regional facilities. Automation, robotics handling sorting, retrieval, and increasingly packing tasks that used to require manual labor, which raises the upfront fixed cost of a facility but lowers the variable cost per unit once installed, exactly the kind of capital expenditure decision that only pays off at sufficient volume. And network design, how many fulfillment centers a company operates and where, since more facilities closer to customers reduce shipping distance and time but also fragment inventory and add fixed operating cost across more locations, a genuine trade off with no universally correct answer, which is why network design remains one of the most actively contested strategic questions inside every large logistics operation.

The Bottom Line

Amazon's own reported numbers, 109.1 billion dollars of fulfillment expense and 102.7 billion dollars of net shipping cost in 2025, on 716.9 billion dollars of net sales, show a fulfillment cost ratio that improved slightly even as the dollar figures kept climbing. The underlying mechanics are not exotic, a large fixed cost base spread across more units gets cheaper per unit, which is exactly why warehouse scale is one of the most durable competitive advantages in retail, and one of the hardest for a smaller competitor to replicate without comparable volume.