Unit economics

Payment and Marketplace Fee Impact on ROAS

Turn the fee actually charged on a matched order population into contribution, allowable CPA, and a break-even ROAS threshold without hiding payment or marketplace costs in a generic margin.

60-second answer

Every order-driven fee lowers the acquisition cost that contribution can support.

Identify the fee base and any fixed component, tier, refund reversal, chargeback, currency-conversion, or marketplace charge. Calculate an effective amount from the same period and order population as the revenue, then include that amount once in the variable-cost model.

Contribution before ads = net revenue - product cost - fulfillment - other variable cost - expected return loss - payment and marketplace fees

Break-even ROAS = net revenue / contribution before ads

Do not use a provider's advertised headline rate as an operating input when the settlement statement includes other order-driven charges. Conversely, do not include the same fee in both the percentage-fee field and another cost field.

Fee mapping

Record what the fee means before converting it into a calculator input.

Fee component	What to capture	Model treatment
Percentage charge	Provider, region, route, category, fee base, and effective dates	Convert the matched-period amount to a percentage of the same revenue basis
Per-order fixed amount	Charge frequency and which orders trigger it	Include once as an order-driven other cost
Tiered or blended charge	Thresholds and observed order mix	Use the same-period weighted effective rate; recheck when mix changes
Refund and chargeback treatment	Whether each component is reversed, retained, or separately charged	Keep it in the fee ledger or return-loss model once, never both
Monthly subscription	Billing period and service scope	Leave outside the per-order comparison unless allocating it by an explicit policy

Stripe documents balance-transaction fields that can support a settlement-ledger review. Shopify profit reports provide commerce cost and profit context. Your contract, marketplace statement, and selected period remain the source of truth for the applicable amount.

Transparent example

The same $100 order moves from 2.33x to 3.23x as fee burden rises.

All figures below are fictional modeling inputs, not provider pricing. Start with $100 net revenue, $40 product cost, $8 fulfillment, $4 other order-driven cost, and a $5 returns allowance. The pre-fee contribution is $43. Compare three fee burdens while holding every other assumption constant.

Fee case	Fee amount	Contribution before ads	Break-even ROAS	Ad cost at 3.50x	Contribution after ads
No payment or marketplace fee	$0	$43	2.33x	$28.57	$14.43
3% effective payment fee	$3	$40	2.50x	$28.57	$11.43
12% marketplace fee	$12	$31	3.23x	$28.57	$2.43

For the 12% case, contribution is $100 - $40 - $8 - $4 - $5 - $12 = $31. Break-even ROAS is $100 / $31 = 3.23x after rounding. At 3.50x, ad cost per order is $100 / 3.50 = $28.57, leaving $31 - $28.57 = $2.43 after ads. The ratio did not change, but the modeled profit buffer did.

Model payment and marketplace fees

Boundary checks

Protect the model from double counting and stale fee assumptions.

Revenue basis: Divide the fee amount by the same net or gross revenue basis used in the contribution model. Do not apply a fee rate from gross sales to a net-revenue model without an explicit adjustment.
One destination: Put a percentage or blended fee into fees. Put a genuine per-order fixed component into other costs. Do not duplicate either component.
Matched period: Recalculate the effective rate when payment route, marketplace category, country, currency, refund mix, order value, or tier changes.
Refund treatment: Keep return loss and non-refunded fees in distinct, documented inputs. A refund may reverse one charge while leaving another in place.
Fixed costs: Monthly software, subscriptions, and baseline overhead do not become per-order contribution costs without a deliberate allocation policy.

Boundary: This model does not determine contractual pricing, tax treatment, accounting recognition, settlement timing, or which fee program applies to a merchant. It uses observed and documented inputs to show sensitivity, not to quote a provider or recommend a payment route or marketplace.

Definition sources

Use settlement evidence and reporting context, then state the model.

Stripe's balance-transaction object documents settlement transaction fields. Shopify profit reports describe product-cost and profit-reporting context. ROAS Break supplies the input mapping, fictional fee cases, contribution method, and double-counting checks.

Stripe balance transaction objectSettlement transaction field context. Checked August 21, 2026.
Shopify profit reportsProduct-cost and profit-reporting context. Checked August 21, 2026.