Your Blended Margin Is Hiding Your Worst Channel: How to Find Your True SKU-Level Profitability

Your ecommerce business might look profitable on paper while some of your best-selling products are quietly losing money.

The problem? Blended margins and standard accounting reports don't always reveal the full cost of selling each product. When marketplace fees, fulfillment expenses, advertising, and returns aren't attributed to individual SKUs, it's difficult to know which products actually contribute to your bottom line.

Understanding SKU-level profitability helps uncover those hidden losses and gives you the financial visibility needed to make better decisions.

Why Gross Margin Doesn't Tell the Whole Story

Gross margin is a useful starting point for evaluating product performance, but it doesn't account for every expense associated with selling online.

For example, QuickBooks Desktop's Sales by Item Summary report shows sales activity and product costs. However, the gross margin reflected in this report doesn't necessarily include marketplace selling fees, fulfillment charges, or advertising expenses.

That distinction matters.

In the Ecom Clinic's illustrative Amazon product catalog, a filter cartridge appeared to be the strongest performer. It had a 74% gross margin and sold 2,200 units.

But once additional selling costs were included, the picture changed dramatically.

The Hidden Costs Behind Your Best-Selling SKU

The filter cartridge sold for an average of $8.49. Its initial gross margin looked healthy, but its actual contribution margin told a different story.

After accounting for referral fees, FBA fulfillment, monthly storage, return processing, and advertising, the product generated a $0.22 loss per unit.

Advertising alone represented 22% of the product's selling price in the example.

Meanwhile, the gravity filter system sold just 310 units but generated 57% of the catalog's total contribution. The filter cartridge represented 51% of units sold while contributing a loss.

The lesson is straightforward: Sales volume and profitability aren't the same thing.

A product can drive significant revenue without generating positive contribution toward the business's other expenses.

How to Calculate SKU-Level Contribution Margin

To understand which products are actually making money, sellers need to look beyond landed costs.

A practical contribution margin calculation is:

Selling Price − Landed Cost − Allocated Selling Fees − Fulfillment Costs − Advertising Costs − Other Applicable Variable Costs = Contribution Margin

This isn't the same as net profit, but it provides a more complete picture of product economics.

Amazon settlement reports contain important information about commissions, fulfillment fees, storage, and other charges. However, summarized settlement information doesn't automatically provide the SKU-level breakdown needed for this analysis.

Sellers need itemized settlement data and accurate fee allocation to understand the true cost of each product.

Webgility helps automate this process by connecting Amazon order data and itemized settlement information with QuickBooks, supporting more detailed accounting and reconciliation.

Five Ways to Address Unprofitable Products

Once you've identified a product with a negative contribution margin, consider several possible adjustments:

1. Review pricing. Evaluate whether a price increase can improve the product's contribution after applicable fees.
2. Reduce advertising costs. Reallocate spending toward products with stronger contribution margins.
3. Optimize packaging. Explore whether changes in weight or dimensions could reduce fulfillment expenses.
4. Test product bundles. Consider multipacks or complementary products that improve order economics.
5. Reevaluate inventory investment. Reduce purchasing or discontinue products when their costs outweigh their strategic value.

A negative contribution margin doesn't automatically mean a product should be discontinued. Some products may introduce customers to more profitable purchases.

The important thing is understanding the tradeoff.

Make Profitability Analysis a Repeatable Process

Start by identifying your highest-volume SKU. Compare its gross margin with its contribution margin after marketplace costs.

Then repeat the analysis for other major products.

Maintain a SKU-level contribution worksheet and revisit it as costs, advertising strategies, and selling prices change.

When you understand which products generate contribution and which consume it, you can make more informed decisions about inventory, advertising, and pricing.

The goal isn't simply to sell more products. It's to understand which sales actually support a healthier ecommerce business.