Harpy Glossary

CM (Contribution Margin)

Amazon & D2C glossary · Harpy Media

CM (Contribution Margin) is what’s left of a sale after every variable cost of that sale: COGS, Amazon fees, fulfilment, shipping, returns, and the ad spend that bought the click. Expressed per unit in dollars or as a percentage of price, it’s the number each sale actually contributes toward fixed costs and real profit.

What is CM?

On Amazon it’s the profitability metric that matters, because gross margin is a costume. A product with a 60% gross margin can contribute negatively once referral fees, FBA tolls, and PPC take their shares. Sellers who run catalogs on gross margin are navigating with a map of a different country.

What belongs in the calculation (everything variable)

The honest per-unit CM on a typical FBA product: landed COGS (product + freight + duties), referral fee, FBA fulfilment fee, monthly storage allocated per unit, expected returns cost (return rate × average loss per return), and allocated ad spend (total ad cost on the ASIN ÷ units sold — the number most people skip). What stays out: genuinely fixed costs (salary, software, the office) — those live below the contribution line. The discipline is including the costs that scale with units and excluding the ones that don’t.

Contribution margin = price − landed COGS − referral fee − fulfilment − returns cost − allocated ad spendPer SKU, recalculated whenever fees, freight, or CPCs move.

What CM unlocks once you have it

Everything strategic: pricing floors (you now know exactly how deep a deal can go), bid ceilings (max profitable CPC falls out of CM × target ACOS), SKU triage (negative-CM products exposed instantly), and portfolio math (which products fund which). It also reframes “my fees are killing me” conversations into specifics: this product’s CM is 14% and its fee stack is the reason; that one’s 31% and deserves the ad budget. Guesswork becomes a table; the table becomes decisions.

In practice

A seller computes true CM across their eight-SKU line and finds their “best seller” contributes $1.90 per unit after ads — while a quiet mid-list SKU contributes $6.40. Ad budget and deal slots move to the quiet earner; the hero gets repriced to cover its true costs. Portfolio profit rises 19% in a quarter on flat revenue — the same sales, better aimed.

⚠️ Watch out. A team uses gross margin for bid ceilings: 45% gross “leaves plenty of room,” so bids run high. True CM after the fee stack is 16%, and the campaign’s breakeven bid was 40% below where it ran. The ads performed beautifully; the unit economics performed a slow bleed.

💡 Harpy tip. Rebuild your CM table the week fee schedules or freight rates change. A stale margin table quietly mis-prices every bid, deal, and reorder you make.

How Harpy Media helps

True contribution margin per SKU is the first model we build on any account — every bid, price, and budget decision downstream inherits it.

CM FAQ

What is contribution margin?

What remains of a sale after all variable costs (COGS, fees, fulfilment, returns, ad spend) — per unit or as a percentage.

How is CM different from gross margin?

Gross margin only subtracts product cost; CM subtracts every variable cost of selling on Amazon — which is why gross margin flatters and CM tells the truth.

Why does CM matter for PPC bids?

Your max profitable CPC is a function of contribution margin — bid above it and every click is a small loss, however good the campaign looks.

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