Which of Your Products Are Actually Making Money?

Most store owners can name their bestseller instantly. Far fewer can name their most profitable product, and in a surprising number of stores they aren't the same thing — sometimes the bestseller is actively losing money.

Why isn't my bestseller my most profitable product?

Because volume and margin are different things, and four costs vary dramatically between products.

Shipping. A heavy or bulky item can cost several times more to ship than a small one. If you charge flat-rate or free shipping, that difference comes straight out of the margin on the heavy product — invisibly.

Returns. Apparel and anything with fit or colour sensitivity returns at far higher rates than, say, consumables. A 25% return rate doesn't just remove the sale; it costs you the outbound shipping, often the return shipping, and the handling.

Ad spend. If most of your advertising drives one product, that product carries the cost. Bestsellers are often bestsellers because you advertise them — which is a cost the sales report never attributes back.

Discounting. Products that only move on promotion have a real margin well below list. Averaged across the year, a permanently-20%-off product is a 20%-lower-margin product.

How do I calculate true per-product profit?

Work down this stack, per product:

Units sold × selling price
− discounts actually given
− returns and refunds
= Net revenue

− landed cost (product + freight in + duty)
= Gross profit

− payment processing fees
− actual shipping cost
− ad spend attributable to this product
= Contribution margin

Contribution margin is the number that matters. It answers: if I sell one more of these, am I better off?

If the answer is no, more marketing makes things worse — which is the single most expensive mistake available to a growing store.

A worked example

Two products, same store:

Swipe to see more →

The candle is 70% of revenue and 12% of profit. It looks like the business. It's actually a very efficient way of converting effort into shipping costs.

Nothing in Shopify's dashboard would tell you this. The candle wins every report it appears in.

What do I do with a low-margin product?

Not necessarily kill it. Options, roughly in order of how often they're the right call:

Raise the price. The most under-used lever in ecommerce. A 10% price rise on the candle above adds $1,400 to contribution margin — more than quadrupling it — and even losing 15% of volume leaves you far ahead.

Fix the shipping. Renegotiate rates, change packaging dimensions, raise the free-shipping threshold, or charge properly for heavy items.

Reduce the ad spend. If it sells anyway, stop paying to acquire the sales you'd get regardless.

Keep it as a loss leader — deliberately. Sometimes a low-margin product brings customers who buy profitable things later. That's a legitimate strategy, but only when it's a decision rather than an accident, and only if you can see the repeat behaviour.

Discontinue it. Last resort, and worth checking it isn't anchoring your range first.

Why doesn't Shopify show me this?

It has some of the inputs — units, price, discounts, refunds — and can hold your cost per item if you enter it. It doesn't know your real shipping cost per order, and it has no idea what you spent advertising a specific product.

So it can get you to gross profit, at best. Contribution margin needs data from your courier and your ad platforms, which live elsewhere.

Pulling those together is exactly what Rev Room does for NZ and Australian stores — Shopify orders, product costs, per-order shipping from Starshipit or GoSweetSpot, and ad spend from Meta, Google and TikTok, resolved down to per-product profit.

You can build the same view in a spreadsheet. It takes a few hours the first time and the numbers usually change how you price.

How often should I check?

Quarterly is enough for most stores. Product economics don't shift week to week, but they do drift — supplier prices creep up, courier rates change, ad costs rise.

Check sooner if you've changed supplier, changed courier, or significantly changed what you're advertising.

The short answer

• Volume and margin are different; bestsellers are often the worst performers
• The four hidden variables are shipping, returns, ad spend and discounting
• Contribution margin per product is the number to rank by
• Low margin usually means raise the price before it means discontinue
• Check quarterly, and after any supplier or courier change

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Related reading: Revenue vs profit · How to calculate your profit margin properly · How to tell when you're spending too much

General information only, current as at 20 August 2026. Figures are illustrative.