In my experience most founders can tell you their overall margin without pausing to think. Ask which product, which channel or which customer is actually paying for the rest of the range, and the answer gets vaguer fast.
A product's real margin sits in what is left after unit cost at your actual order volume, packaging, the channel's fee or retailer terms, returns and breakage, and the cash value of any discount taken. Gross margin will not show you that. Contribution margin, calculated per line and per channel, will.
My experience is that the line that sells the most is rarely the line that earns the most. That gap is not a rounding error. It is where a business quietly funds its least profitable decisions with its most profitable ones, without anyone choosing to do that on purpose.
Revenue by line is not profit by line
A monthly report built around revenue tells you what sold. It tells you almost nothing about what was left once everything that sale actually cost has been taken out. Two products can sit next to each other on a top-line report showing similar revenue and be worlds apart underneath it — one earning a healthy contribution, the other barely covering the cost of getting it to the customer.
The fix is not a bigger spreadsheet. It is a different question, asked line by line, channel by channel and, where the data allows it, customer by customer: after every real cost of selling this unit is taken out, what is actually left, in cash, not only as a percentage.
Packaging and unit cost at the volumes you actually order
A unit cost quoted at a supplier's minimum order quantity is not the unit cost the business runs on. The price on the sample order and the price once you are ordering at the volume the business actually sells are frequently different numbers, and a range priced against the sample-order cost tends to find its real margin sitting lower than planned.
Packaging is the part of this I see underpriced most often, because it is quoted separately from the product and rarely re-quoted once the pack changes: a new closure, a heavier glass jar for a premium reposition, a printed box instead of a plain one. Each decision is defensible on its own. Costed against the margin the product actually needs to hold, several of them together can be the difference between a line that earns its place in the range and one that does not.
Channel cost: what a marketplace or a retailer's terms really take
A marketplace's fee schedule is public, and it is worth reading in full rather than assuming a flat percentage. Amazon's own published UK seller pricing states that referral fees for most categories sit between 8% and 15% of the total sale price, calculated on the item price plus shipping, with separate fulfilment and subscription fees on top of that (sell.amazon.co.uk/pricing). That is Amazon's own schedule, not a marketplace-wide average, and every platform publishes its own; the discipline is reading the actual number for your category rather than budgeting against a guess.
A retailer's terms take a different shape but the same bite: a trade discount off the retail price, sometimes a marketing or listing contribution, and in many arrangements the right to return unsold stock rather than the brand keeping it as a firm sale. A wholesale line can look perfectly healthy on the trade price until the cost of actually servicing it, minimum order runs, marketing contributions, stock returned under those terms, is costed back against it. At that point it can turn out to be funded by the direct channel rather than funding it.
The cost of holding stock that is not moving
A production run large enough to hit a better unit-cost break looks like a saving on the invoice — it can also tie up cash for a year rather than a quarter. Every month that stock sits in a warehouse it is still costing rent, insurance and the risk that the packaging or the formulation reaches the end of its shelf life before the last unit sells. None of that shows up as a cost on the day of the production run. It shows up later, as a write-off or a deep discount to move it before it expires, and by then it reads as a pricing problem rather than what it actually was: a stock decision made against a unit-cost saving that never accounted for the cost of the cash it tied up.
Promotional depth: what a discount actually costs
The maths is worth doing properly, because it is not intuitive. Take a simple illustration: a product priced at £100 with a cost of £55 carries a 45% margin. Discount it by 20% and the price falls to £80, but the cost has not moved, so the cash margin falls to £25, or 31% of the new price. The price dropped by a fifth. The cash margin dropped by nearly half. The lower the margin a product started with, the worse this arithmetic gets, which is exactly why the products most often put on promotion are frequently the ones that could least afford it.
The line that looks successful because it sells the most
I spent almost twenty years working on some of the biggest brands in beauty and luxury — L'Oréal Group and Coty. That is where I learned to read a report like this one. Nothing that follows is a description of any business I worked in, and it is not a comment on how any of them was run.
The mechanism is straightforward enough. The product that takes the most warehouse space, the most marketing spend and the highest revenue line in a monthly report is not always the one earning the most. Sometimes it is the one everyone in the business is proudest of — and it is being carried by lines nobody talks about. The same pattern shows up in customers: the one who orders most often is sometimes only ever buying at a discount, which is a different thing from being your best customer.
That is not a failure of the product or the customer. It is a failure of a report that only ever showed revenue, and never showed what was left once everything the sale actually cost had been taken out.
What to calculate instead of what to feel
Start with contribution, not gross margin, and calculate it per product, per channel and, where the data exists, per customer type: revenue, less unit cost at the volume you actually order, less packaging, less the channel's real cost, marketplace fee or retailer terms, less a provision for returns and breakage where the channel generates them, less the actual value of any promotional discount taken, not the list price. What is left is the number that matters, and it is very often not the number the monthly revenue report has been training you to look at.
That is a specific, answerable question, not a full review of the brand, and it is exactly the kind of narrow diagnostic work Brand Intelligence is built to do on its own, before it gets folded into anything bigger.
FAQ
What is the difference between gross margin and contribution margin? Gross margin is revenue less the cost of the product. Contribution margin goes further and takes off everything else the sale itself causes: packaging, the channel's fee or terms, and a fair share of returns or breakage. Gross margin can look healthy while contribution margin is thin or negative.
Why does a best-selling product sometimes make the least money? Because revenue and profit are measured differently, and a report built around revenue alone cannot show the difference. A product can post the highest sales figure in the range and still carry the highest packaging cost, the deepest promotional discount or the most returns, all of which come off before anything is actually earned.
How often should a product brand review margin by line? At minimum, whenever a supplier price changes, a channel's terms change, or a promotional calendar is being planned, because all three move the real number without necessarily moving the price on the shelf. Reviewing it only once a year means finding out how much has shifted after the fact rather than before it.
Is a marketplace worth the fee it charges? It depends entirely on what the fee actually is for your category and what the channel replaces, which is why reading the published fee schedule is the first step, not the last one.
If you cannot say which product, channel or customer is actually paying for the rest of the range, that is not a sign the business is doing badly. It is a sign the question has not been asked properly yet, and it is a narrower piece of work to answer than most founders assume. Get in touch to talk through where to start looking.