The free-returns promise on most American product pages was underwritten at a diesel price that has since stopped existing. On-highway diesel averaged $3.809 a gallon in the last week of February. For the week ending 21 September the same U.S. Energy Information Administration series put the national average at $6.529, a rise of 71%. The thresholds have not moved a cent, so the difference will be kept inside fourth-quarter gross margin, where nobody has to announce it.

One half of that promise is indexed; the other is typed. FedEx resets its ground fuel surcharge every week, read off the national diesel average, and the new number takes effect on a Monday without anyone’s consent. A free-shipping threshold moves only when a merchandiser agrees to risk conversion. The carrier’s price follows the fuel; the retailer’s promise follows a meeting.

Amazon reached for the same lever in the spring, adding a 3.5% surcharge to every FBA fulfillment fee. Marketplaces reprice on notice; storefronts reprice on courage.

The national average also hides where the exposure sits. Diesel in California ran $8.246 a gallon last week against $6.177 on the Gulf Coast. A single threshold, set in dollars, underwrites deliveries whose fuel cost varies by a third depending on which state the van is in.

The figure the trade keeps quoting is the consumer’s. Gas is up roughly 50% since the war began on 28 February, Modern Retail reported on Monday; Wisconsin added 61 cents in eight days. Shoppers meet that number at the pump, and no parcel is billed against it. Ground parcels are billed against diesel, which has climbed twenty-one percentage points further.

The people who move the boxes assume somebody will absorb it. Fuel surcharges have hit close to near-record highs — FedEx’s domestic figure now runs 32.25%, Modern Retail reported. It used to be a line “that you didn’t even look at,” Matt Hertz of Third Person says. “So it’s historically been absorbed.” Much of the holiday supply chain, he adds, was bought before this leg up in prices. The inbound was hedged by accident; the outbound was not hedged at all.

A few brands have tried moving the number, and the result is already on the record. Barnes & Noble lifted its free-shipping floor from $50 to $60 in the spring. Joe & Bella took its own from $75 to $100 and put it straight back: “Our site conversion absolutely tanked,” co-founder Jimmy Zollo told Modern Retail. The threshold is not a cost input. It is a price, and it is the one price nobody moves in November.

A free return is the only freight in retail that travels twice and sells nothing.

The volume behind that sentence is not marginal. Retailers projected that 19.3% of online purchases would come back last year, part of $849.9 billion expected across every channel, on National Retail Federation and Happy Returns figures. A fifth of what goes out comes back, and it comes back at September’s diesel against a promise written in February.

None of this arrived unannounced. The Postal Service filed an 8% parcel fuel surcharge in April, proposed to run through 17 January 2027 pending Postal Regulatory Commission approval. The Retail Industry Leaders Association warned at the time that it would put pressure on free-shipping models. Five months of notice produced a few higher thresholds and not one revised returns policy. The promise will be rewritten in January, when it costs nothing to rewrite.