Two sellers offering the same product at the same price can deliver very different experiences. The difference is usually which fulfilment method sits behind the listing.
The two routes an order can take
A seller can hold stock themselves and dispatch each order on receipt, controlling packing, carrier choice and timing directly.
Alternatively they can send inventory to the platform's warehouses in advance, after which the platform picks, packs, ships and handles returns on their behalf.
The second route costs a fee per unit for handling plus a charge for storage, and those costs are built into whatever price the seller then lists.
How the fees are calculated
Handling fees are driven by size and weight bands, so a small increase in packaging dimensions can push an item into a costlier band entirely.
Storage is charged by volume over time, which penalises slow-moving stock and rises sharply during peak periods when warehouse space is scarcest.
Long-term storage surcharges apply to inventory that lingers, which is why sellers discount aggressively rather than let stock sit past those thresholds.
What the buyer notices
Platform-fulfilled orders qualify for the fastest delivery options and are covered by the platform's own returns process, which is generally the simpler route.
Seller-fulfilled orders depend on that individual merchant's operation, so dispatch times, carrier quality and returns handling vary considerably between them.
Neither is inherently better. A specialist seller shipping their own goods may pack more carefully, while a platform warehouse is more consistent about speed.
Why the same product costs different amounts
A seller using platform fulfilment carries per-unit costs a self-shipping seller does not, so their price is often higher for the identical item.
The difference is not margin. It is the cost of the delivery promise and the returns handling attached to that particular offer.
Comparing offers therefore means comparing the delivered proposition rather than the product price, since the two offers are not selling quite the same thing.
Where inventory is pooled
Some programmes allow identical units from different sellers to be stored together, so the item dispatched may not be the one that seller sent in.
This improves delivery speed by shipping from the nearest warehouse, but it weakens the link between the seller chosen and the physical unit received.
It is one reason counterfeit goods can reach buyers who ordered from a reputable seller, and why brands press platforms to keep their stock separated.