Unit Economics — Does Each Sale Make Money?
By Pritesh Yadav 9 min read —
Here is a question that quietly decides whether a business lives or dies: when you make one sale, do you end up with more money than you started with? It sounds obvious. It is not. Plenty of fast-growing, exciting companies have answered "no" without realising it — and the faster they grew, the faster they went broke. This chapter teaches you to answer that question with confidence, using nothing more than arithmetic you already know.
Unit economics simply means looking at the money math of one unit — one sale, one order, one customer — instead of the big blurry total. The total can hide a leak. A single unit cannot.
Analogy: A bucket factory can report ₹50 lakh in sales and still be sinking, if every bucket it sells has a hole that costs ₹110 to make and sells for ₹100. The annual report looks busy and impressive. Each bucket is bleeding ₹10. Unit economics is the act of picking up one bucket and checking for the hole.
The vocabulary ladder — build it in this exact order
Each term below builds on the one before it. Don't skip; the magic is in how they stack.
- Revenue (per unit)
- The price one customer pays for one purchase. ₹500 for a subscription box this month. Just that — not the yearly total.
- COGS — Cost of Goods Sold
- The direct cost to make or deliver that one thing: raw materials, the ink and paper for a printed card, the cloud-server cost to serve one user. It excludes fixed overhead like office rent and salaries — those don't go up when you sell one more unit.
- Gross margin
(Revenue − COGS) ÷ Revenue.Answers: "Is the product itself worth making?" A ₹500 product costing ₹150 to make has a gross margin of 70%.- Contribution margin
- Revenue minus all variable costs — COGS plus shipping, payment-gateway fee, returns, and the marketing spend you can attribute to that order. Answers the sharper question: "Is it worth selling this, through this channel, at what it costs to win the customer?" Contribution margin is always ≤ gross margin.
Common mistake: Treating gross margin as "profit per sale." It isn't. A real direct-to-consumer product can show a gorgeous 70% gross margin yet only 19.5% contribution margin once shipping, ad spend, returns, platform fees and payment fees are subtracted. That gap — roughly 50 points — is exactly where founders fool themselves into thinking a losing business is winning.
PRICE the customer pays (Revenue) ₹500 − COGS (make/deliver it) −₹150 → Gross margin = 70% − shipping −₹30 − payment-gateway fee (~2% + GST) −₹12 − returns / refunds (averaged) −₹20 − marketing attributed to this order −₹40 ─────────────────────────────────────────────── = CONTRIBUTION MARGIN (the honest number) ₹248 → ~49.6%
Adding the customer dimension: CAC, churn, and LTV
One sale is the start. Most real money comes from a customer who comes back. To measure that, we need three more terms.
- CAC — Customer Acquisition Cost
- Total sales + marketing spend in a period ÷ new customers won in that period. Crucially this includes salaries of the people doing sales/marketing, not just the ad bill. Founders who count only ad spend understate CAC and feel richer than they are.
- Churn rate
- The % of customers (or revenue) you lose each period. If 5% leave every month, the average customer life ≈ 1 ÷ churn = 1 ÷ 0.05 = 20 months.
- LTV — Lifetime Value
- The total contribution margin one customer generates across their whole relationship with you. A simple, widely used formula (popularised by David Skok):
LTV = ARPU × gross margin ÷ churn rate.ARPU is "average revenue per user per period."
Common mistake: Measuring LTV on revenue instead of margin. If you bring in ₹7,000 of revenue but ₹4,000 of it is cost, the customer is worth ₹3,000 of value, not ₹7,000. Always base LTV on contribution margin, or you will badly overstate every customer.
The two headline ratios — the make-or-break verdict
Combine the customer's value (LTV) with what they cost to win (CAC) and you get the two numbers investors and seasoned founders judge a business on.
1. LTV : CAC ratio — the magnitude check
This famous benchmark of ~3:1 comes from David Skok (Matrix Partners) in SaaS Metrics 2.0 around 2010, derived from mature public SaaS companies like HubSpot, Salesforce and NetSuite.
- < 1:1 — you lose money on every customer. Stop.
- ~1–2:1 — fragile; one bad month wipes you out.
- ~3:1 — the healthy floor.
- 5:1 and above — strong... but possibly a warning that you are under-spending on growth and leaving money on the table.
2. CAC payback period — the speed check
CAC ÷ monthly contribution margin per customer. It measures how many months until you get your acquisition money back. Two businesses can both be 3:1, yet a 6-month payback is dramatically healthier than an 18-month one — the first recycles its cash into the next customer long before the second has even recovered half. A healthy SaaS target is a payback under 12 months.
Key takeaway: Ratio tells you the magnitude of the win; payback tells you how long your cash is at risk. You need both. A great ratio with a 20-month payback can still starve you of cash and kill you.
Example: A subscription box.
Price ₹500/mo; COGS ₹150 → contribution ₹350/mo (70%).
Monthly churn 5% → lifetime = 1 ÷ 0.05 = 20 months.
LTV = ₹350 × 20 = ₹7,000. CAC = ₹2,000.
LTV:CAC = 7,000 ÷ 2,000 = 3.5:1 ✓
Payback = ₹2,000 ÷ ₹350 = ~5.7 months ✓
Now break it. Churn doubles to 10% → lifetime halves to 10 months → LTV = ₹3,500 → ratio crashes to 1.75:1 (fragile), with the same CAC and the same product. Churn sits in the denominator, so a small worsening swings LTV violently. Fixing churn is usually your highest-leverage move.
Price ₹500/mo; COGS ₹150 → contribution ₹350/mo (70%).
Monthly churn 5% → lifetime = 1 ÷ 0.05 = 20 months.
LTV = ₹350 × 20 = ₹7,000. CAC = ₹2,000.
LTV:CAC = 7,000 ÷ 2,000 = 3.5:1 ✓
Payback = ₹2,000 ÷ ₹350 = ~5.7 months ✓
Now break it. Churn doubles to 10% → lifetime halves to 10 months → LTV = ₹3,500 → ratio crashes to 1.75:1 (fragile), with the same CAC and the same product. Churn sits in the denominator, so a small worsening swings LTV violently. Fixing churn is usually your highest-leverage move.
The most expensive lie in business: "we'll make it up in volume"
If your per-unit economics are negative, growth doesn't save you — it accelerates the funeral. The canonical case is MoviePass.
Example — MoviePass (2017–2020): Parent company Helios & Matheson cut the price to $9.95/month for up to one movie a day. But MoviePass paid theaters $12–$15 per ticket. So it charged $9.95 and paid out $12+ — a negative contribution margin on every active customer. The result was perverse: the more people used the service, the faster it died. It rocketed to 3M+ subscribers (looked like a rocket ship), burned $21.7M in a single month, shut down in 2019, and the parent filed Chapter 7 bankruptcy in 2020 — over $1.5B destroyed.
Best practice: Compare this with Amazon, which famously "lost money for years." The difference is categorical: Amazon's per-transaction (contribution) economics were positive; it was deliberately spending on fixed investments — warehouses, software — ahead of scale. Losing money on fixed bets you'll earn back is investing. Losing money on every single transaction is just subsidising your own demise.
How to improve each lever (the offense playbook)
| Lever | How to pull it | Notes |
|---|---|---|
| Raise revenue / ARPU | Price increases, upsells, cross-sells, tiers, bundles | Usually the single highest-leverage move — most founders under-price out of fear. |
| Cut COGS | Better supplier terms, volume discounts, cheaper-to-serve infra, automation | Directly widens both gross and contribution margin. |
| Lower CAC | Shift toward organic, referral, content, word-of-mouth; kill bad channels | Analyse contribution margin per channel — one Google campaign can be profitable while another bleeds. |
| Reduce churn | Better onboarding, stickier product, annual plans | Highest LTV leverage. Aim for negative net churn (existing customers expand spend faster than others leave). |
| Shorten payback | Annual upfront billing, lower-CAC channels | Recovers cash faster so you can reinvest sooner. |
Key takeaway: If you ever achieve negative net churn, the simple LTV formula breaks (lifetime becomes effectively infinite). At that point you graduate to Skok's advanced DCF version, which accounts for expansion growth and a discount-rate deflator. That's a wonderful problem to have — but don't reach for it until your churn data is genuinely stable.
India-specific costs you must bake in (June 2026)
For an Indian founder, two real variable costs frequently get left out of contribution margin — and both reduce your honest per-sale profit.
- GST. Once your aggregate turnover crosses the registration threshold, GST becomes a real cost layer on your pricing. For FY 2025–26: Goods — ₹40 lakh; Services — ₹20 lakh in normal-category states. Special-category states are lower: ₹20 lakh (goods) / ₹10 lakh (services). Below the threshold your net unit economics quietly differ from after you cross it — model both.
- Payment-gateway fees. Indian gateways (Razorpay, PayU, etc.) typically charge around 2% + GST on that fee. On a ₹500 sale that's roughly ₹12 — small per order, but it belongs in contribution margin, not ignored.
Common mistake (honesty note): The 3:1 rule was never meant for pre-product-market-fit or seed-stage businesses, yet it gets applied everywhere. Early on, your CAC and churn numbers are tiny, noisy and unreliable — don't over-fit to them. And remember: LTV is a forecast built on an assumed churn rate, not a fact. Treat it as an estimate, and revisit it as real data matures. None of this is a get-rich hack; it's patient measurement that compounds.
Key Takeaways
- One unit reveals the truth the total hides. Always ask whether a single sale ends with you holding more money than you started with.
- Contribution margin > gross margin as the honest per-sale number — it subtracts shipping, fees, returns and acquisition cost. A 70% gross-margin product can be a 19.5% contribution-margin business.
- Judge customers on two ratios: LTV:CAC (target ~3:1 for magnitude) and CAC payback period (target <12 months for speed). You need both.
- Churn is the silent killer — it sits in the LTV denominator, so reducing it is usually your highest-leverage move; doubling churn can halve customer value overnight.
- Growth amplifies your unit economics, good or bad. MoviePass grew to 3M users and died because each customer lost money. "We'll make it up in volume" is the most expensive lie in business.
- In India, bake in GST (₹40L goods / ₹20L services thresholds, FY25–26) and ~2%+GST gateway fees as real variable costs before you trust any margin number.