Most ecommerce growth charts go up and to the right. The question is whether that growth is real (compounding) or rented (paid acquisition driving a vanity line). Three numbers tell you the difference.
Walk into a DTC board meeting and the revenue chart goes up and to the right. Walk into the same meeting a year later and the chart still goes up, but the founder looks tired. Ecommerce growth rents easily — pour spend into Meta, get revenue back, plot the line, call it growth.
The question is whether that growth is real. Three numbers answer it.
Growth is "real" when the business compounds — each cohort produces lifetime value above acquisition cost, repeat revenue grows as a percentage of total, and the business gets more efficient as it scales. Growth is "rented" when the business depends on continuously increasing paid spend to maintain the line.
The three numbers that tell them apart:
The share of monthly revenue from customers who have purchased before. The trajectory matters more than the absolute number:
Healthy DTC sits at 40–55% repeat revenue and rising. Subscription-led businesses can hit 70%+. Below 25% means you're effectively running a paid-acquisition business with an ecommerce skin on top.
Average CAC tells you what acquisition has cost on average. Marginal CAC tells you what the next customer will cost. Pull CAC by acquisition cohort (Q1 customers, Q2 customers, etc.) and trend it:
| Cohort | CAC (paid) | Conclusion |
|---|---|---|
| Q1 | £42 | — |
| Q2 | £48 | +14% (some channel saturation) |
| Q3 | £61 | +27% (warning) |
| Q4 | £78 | +28% (channel exhaustion or competition) |
If marginal CAC is climbing faster than 6-month LTV is climbing, paid growth is rented and getting more expensive. Shopify's State of Commerce tracks this trend at platform level — most DTC categories saw 2024 marginal CAC up 15–25% YoY.
The cleanest single metric for "is this customer profitable, on average, after everything attributable":
Contribution margin = (Revenue × Gross Margin) − Acquisition Cost − Variable Operating Cost
Variable operating cost = shipping, transaction fees, returns processing — anything that scales per-customer. Fixed costs (rent, salaries, software) sit above the contribution margin line.
If contribution margin per customer is positive AND rising, growth compounds. If it's positive but falling, you're scaling toward a ceiling. If it's negative, every new customer makes the loss worse.
One of those is fine, two is borderline, three+ means the model is renting.
Two paths. Pick one based on cash position:
Workable if cash flow allows a 60–90 day "no-growth" period. During the pause: rebuild lifecycle flows, tune the second-purchase trigger, run the lifecycle audit honestly. Acquisition resumes once repeat revenue % is rising again. Total revenue dips in the short term, contribution margin improves, the business is healthier coming out.
If a pause isn't viable, shift paid spend incrementally — 20% of the highest-CAC channel's budget moves to lower-CAC, higher-LTV channels each quarter. SEO and organic content take longer to compound but produce stickier customers. Email-driven referral programs convert at 1.5–2.5× the rate of paid.
Pull the three numbers above for the last 4–6 quarters. If repeat revenue % is rising, marginal CAC is stable or falling, and contribution margin is positive and stable — real. If two of three are deteriorating — rented.
Paid acquisition is fine. Paid acquisition as the only lever is bad. Healthy DTC has paid as one channel inside a mix that includes organic, email, referral, and brand. The dependency ratio is what matters — if 70%+ of acquisition comes from one paid channel, the business is fragile to that channel's pricing.
Highly category-specific. Mature DTC categories (skincare, supplements): 15–35% YoY is healthy. Emerging categories: 50–100%+ for the first few years. Below 10% YoY for 2+ consecutive years usually signals product-market fit issues, not growth issues.
When first-to-second purchase rate is below 25% AND average orders per customer is under 1.6. At that point, every pound spent on acquisition fills a bucket with a hole. Fix the bucket first.
First-to-second purchase rate. Moving it from 30% to 45% lifts LTV by ~25%, payback period shortens, and you can spend more on acquisition profitably. Almost everything else (loyalty programs, channel expansion, brand investment) is downstream of this one number.
Qwrki doesn't run growth as "spend more on Meta." We run it as one operating layer covering acquisition, retention, lifecycle, and analytics — where the three numbers above sit in your live dashboard and drive what we do next week. If your growth chart is going up but the founder is tired, that usually means it's rented. Book a call — we'll run the three-number audit honestly.
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