Marketplace Unit Economics: How to Calculate Profit per SKU
Practice4 minInnovialabs editorial team
In short
Profit per unit is the actual selling price minus every cost one sale creates, including returns, ads and taxes; calculate it per SKU, or best-sellers can hide losses.
The short answer
Unit economics is the profit you make on one sold unit. The formula is simple: the price the customer actually pays minus every cost caused by selling that unit. The hard part is not the formula but remembering every cost line and allocating shared costs (advertising, storage, returns) to a specific SKU.
Calculate it for each SKU separately. The average margin of a store almost always looks fine and hides products that sell well but lose money.
What goes into the cost per unit
| Cost line | How to calculate per unit |
|---|---|
| Cost price | Purchase + shipping to your warehouse + packaging and labeling |
| Marketplace commission | Category rate applied to the selling price (use the platform's current fee schedule) |
| Logistics | Delivery to the platform's warehouse and to the customer, by the tariff for the item's size |
| Storage | Monthly storage fee divided by units sold that month |
| Returns | Reverse logistics and losses on damaged items, multiplied by the return rate |
| Advertising | Promotion spend on the SKU divided by its sales |
| Taxes | Depends on your tax regime: on revenue or on profit |
| Acquiring | If the platform deducts it separately, a percentage of the price |
The selling price is the amount after discounts and promotions, not the listing price. If you join sales events, use the actual average price for the period.
Step-by-step calculation
- Export the monthly sales and deductions report from the seller account.
- For each SKU, count units actually bought (not returned) and real revenue.
- Add cost price from your accounting system.
- Allocate platform deductions to SKUs: commission and logistics are usually listed per line, while storage and penalties sometimes need manual splitting.
- Calculate returns: what delivery of returned units cost and how many cannot be resold.
- Assign advertising to the SKUs it was spent on.
- Subtract tax to get profit per unit and margin — profit divided by selling price.
An example in arbitrary units (illustrative figures, not real platform tariffs):
| Metric | SKU A | SKU B |
|---|---|---|
| Selling price | 100 | 100 |
| Cost price | 40 | 45 |
| Commission | 15 | 15 |
| Logistics and storage | 12 | 20 |
| Returns | 3 | 10 |
| Advertising | 5 | 18 |
| Tax and acquiring | 8 | 8 |
| Profit per unit | 17 | −16 |
Both products have the same price, but the second one is bulkier, gets returned more often and stays at the top only thanks to ads. Every sale of SKU B reduces the store's profit.
How to spot SKUs that sell but lose money
- Sort SKUs by sales volume and put profit per unit next to it. Revenue leaders with negative profit are the first to investigate.
- Watch the ad share of price. If a product does not sell without ads and does not pay off with them, the problem is the price or the product itself.
- Check dimensions. Bulky and heavy items are often eaten by logistics and storage.
- Track the buyout rate. For clothing and footwear, returns can shift the picture more than commission.
- Find slow-moving stock. Slow SKUs accumulate storage fees for months.
What to do with loss-making SKUs
- Revisit the price or participation in promotions.
- Lower the cost price: another supplier, packaging, batch size.
- Change the fulfillment model: store in your own warehouse or in the platform's — calculate both.
- Cut or retune advertising.
- Remove the product if it is not needed as a traffic driver for other purchases.
Common mistakes
- Calculating profit as price minus purchase and commission, forgetting logistics and returns.
- Using the listing price instead of the actual price after discounts.
- Relying on outdated tariffs: platforms change them regularly.
- Splitting advertising evenly across the whole catalog.
- Calculating once and never updating it.