A free-shipping promise in a ChatGPT ad still leaves someone paying the carrier. If the advertiser compares reported cost per purchase with product margin alone, that delivery expense can make an apparently acceptable campaign uneconomic. The problem is especially visible when an offer attracts small baskets just above a free-shipping threshold.
This guide develops an internal costing method for advertising on ChatGPT. It does not estimate market shipping rates or predict achievable acquisition costs. Its purpose is to give marketing and finance a shared number against which to assess purchases with the same economic definition.
Identify the part of delivery the business funds
Define the shipping subsidy as the merchant’s delivery cost less the shipping charge actually paid by the customer. Use one currency and consistent tax treatment. For example, if the business evaluates contribution excluding VAT, both the carrier cost and the customer’s shipping payment must be on that basis. Comparing a tax-inclusive customer charge with a tax-exclusive cost distorts the subsidy.
Decide what belongs in the delivery line. Carrier charges, fuel adjustments and relevant oversize surcharges may belong there. Picking, packing and packaging can remain separate order costs. Every expense needs one home. If a fulfilment provider’s order fee already includes packaging, subtracting packaging again understates the amount available for advertising.
The customer’s shipping payment also needs one home. Starting with merchandise revenue alone means subtracting the net subsidy. Starting with total revenue including shipping means subtracting the full delivery cost. These approaches reconcile when the underlying amounts are consistent; mixing them creates an artificial margin.
Calculate the allowance with a complete order
Consider a hypothetical order in Swedish kronor, with every amount excluding VAT. Merchandise revenue after discounts is SEK 800. Product cost is SEK 360 and other variable order costs are SEK 40. The contribution before shipping and advertising is therefore SEK 400. Delivery costs SEK 70, while the customer pays SEK 20 for it.
The shipping subsidy is SEK 50. That leaves SEK 350 before advertising. Suppose the business wants to retain SEK 120 per order toward fixed costs and its desired operating result. The internal media CPA ceiling becomes SEK 230: 400 minus 50 minus 120. Retained contribution is not net profit because fixed expenses still need to be covered.
Check the result using total revenue. Revenue including the shipping payment is SEK 820. Subtract product cost of 360, other costs of 40, carrier cost of 70 and advertising of 230. The remaining contribution is 120. This second route catches both missing costs and shipping revenue counted twice. The break-even CPA guide explains the wider contribution model.
Free shipping removes a real revenue line
If the same order receives free shipping, the subsidy rises to SEK 70. Holding every other assumption constant, the CPA ceiling falls to SEK 210. The difference is SEK 20, exactly the customer payment that has disappeared. This does not establish whether free shipping is a good offer; it establishes the different cost constraint the offer must meet.
The offer may also change basket size. A customer who adds another item to qualify for free delivery brings the contribution from that item, not its entire selling price. Recalculate product costs and any additional handling before deciding that the larger basket pays for shipping.
When a ChatGPT campaign combines a price reduction with free delivery, treat both effects explicitly. The discount and margin calculation helps separate lost merchandise revenue from merchant-funded shipping. Assuming future repeat purchases will cover a weak first order is a separate business hypothesis and needs its own evidence.
Weight the subsidy by a useful order mix
The store-wide average may be a poor fit for a specific ChatGPT campaign. An ad can point to a different product family, basket size or delivery destination. Start with segments that the business can identify reliably in its order records, such as standard parcels versus oversized parcels, or paid shipping versus free shipping.
In a second hypothetical scenario, 60% of orders have a SEK 50 subsidy and 40% have a SEK 70 subsidy. The weighted subsidy is 0.60 times 50 plus 0.40 times 70, which equals SEK 58. With the same SEK 400 contribution before shipping and SEK 120 retention requirement, the average media CPA ceiling is SEK 222.
This shortcut works only because the other order economics are identical in the example. If free shipping mainly applies to larger orders, calculate each group’s complete contribution first and then weight by order count. Taking a simple average of two ceilings ignores how many orders each group represents.
Shipping changes the room for advertising
- Customer pays SEK 20
Shipping cost 70 less shipping revenue 20 gives a subsidy of 50. CPA ceiling: 400 − 50 − 120 = SEK 230.
- Free shipping
The subsidy equals the full shipping cost of SEK 70. CPA ceiling: 400 − 70 − 120 = SEK 210.
- A mixture of both
60% customer-paid shipping and 40% free shipping gives a subsidy of SEK 58. CPA ceiling: SEK 222.
Add delivery exceptions without counting them twice
Split shipments, failed collection and replacement deliveries can create additional costs. Keep an expected exception cost separate where there is a defensible basis for its frequency. If, hypothetically, 10% of orders require another SEK 40 shipment, expected extra delivery cost is SEK 4 per order. That reduces the advertising allowance by SEK 4 unless it is already included in the ordinary shipping estimate.
Return shipping requires the same discipline. An existing returns allowance may already contain it. Record what the allowance covers and the observation period behind it. The return-rate sensitivity guide is useful when mature return data are unavailable and several outcomes must be considered.
Compare against purchases with the same definition
OpenAI Reporting defines CPA using spend and conversions. Confirm that the conversion being evaluated is the purchase outcome used in your costing model. A lead or registration cannot be compared directly with contribution from a shipped order.
OpenAI Conversion Tracking explains purchase-event reporting. The merchant’s actual shipping subsidy still comes from order and cost records. Attributed sales are not a completed contribution calculation.
Keep a dated working sheet showing the carrier agreement, customer charges, order mix and calculation owner. Revise it when the shipping promise changes. Then a movement in acceptable CPA can be traced to delivery economics rather than mistaken for a change in advertising efficiency.
Sources and scope
Calculate how the merchant-funded portion of delivery reduces the acquisition-cost allowance for purchases attributed to ChatGPT advertising.
Working methods and examples are editorial suggestions. Check current platform requirements and available features before implementation.