Why Revenue Is Up but Your Bank Balance Isn't
Revenue is higher than last year, yet the money left in the bank hasn't moved, and many solo online sellers can't tell which part of the business is actually getting more profitable. Looking only at company-wide revenue growth won't answer that question. Growth tells you whether sales went up, but not how much of those sales was worth keeping. The answer lies in the cost structure of each segment and category. Today we'll use Coupang's fiscal 2025 10-K filing as our textbook and learn how to read the reasons behind an improving cost-of-sales ratio.
The Concept: A Cost Ratio Only Makes Sense When You Split It
The cost-of-sales ratio is the share of revenue consumed by cost of goods sold. When it falls, the same revenue leaves more money in your hands. But if you run several channels or product lines, the company-wide ratio can't show you where the improvement happened. If one segment's ratio improves sharply while another stands still, the overall figure blends the two movements into a single average. So after checking the total, split it once more by segment or category, and only then does the real source of improvement show up. Do it in the wrong order and you'll miss the segment that is actually getting better and end up tinkering with the wrong one.
Reading the Coupang Case: 1.6 Percentage Points Hidden Behind 0.2
Coupang's total net revenue grew 14%, from $3,026.8 million to $3,453.4 million. That growth came from two things working together: the number of customers rose 8–10% each quarter, and revenue per customer rose 3–7% each quarter. In other words, volume and price moved at a similar pace. It wasn't a case of adding new customers alone or of squeezing more out of existing ones; both levers worked evenly.
On the cost side, the company-wide cost-of-sales ratio improved by just 0.2 percentage points, from 70.8% to 70.6%. On its face, that looks like almost no change. But walk through where the improvement came from, step by step, and the story changes.
To sum up: the products customers buy shifted toward higher-margin categories, and Coupang's in-house logistics business (FLC) pushed that shift along, improving the cost ratio of its core Product Commerce segment by a full 1.6 percentage points. Once blended with the other segments, that large gain showed up in the company-wide figure as only 0.2 points. Meanwhile, the Developing Offerings segment, which grew a striking 38%, came with a caveat: it still has a low-margin structure. On growth alone it looks like the standout, but how much it contributes to profit has to be judged separately.
Applying It to Your Business: Calculate by Channel and Product Line
Here is how to check for yourself. First, calculate your overall cost-of-sales ratio once. Then calculate the ratio separately for each sales channel, or for each product category. If you run both your own online store and an open marketplace, write down the cost ratio for each channel side by side. If you sell several product lines, work out the ratio of purchase cost to selling price for each one. That reveals which channel or product line is really pushing your margin up, something the overall number never shows. If a product line's revenue is climbing fast but its cost ratio is flat or even getting worse, ask again whether it contributes to profit as much as it contributes to sales growth. Conversely, if a line with a small share of revenue shows a clearly improving cost ratio, that is a reason to put more weight behind it.
Wrapping Up: Today's To-Do
There is just one thing to do today. Take your revenue and costs for the last three months, split them by channel or product line, and calculate each cost ratio. Reading the reasons behind an improving cost-of-sales ratio starts not with a single overall number, but with several split-out numbers laid side by side.
