Unit Economics 101: CAC, LTV, and Payback Period
Unicorn Rivals Team
Why Unit Economics Matter
You can have growing revenue and still die — if each customer costs more to acquire and serve than they ever pay back.
Unit economics asks: Does one more customer improve or harm the business? It's the bridge between burn rate and product-market fit.
New to startups? Startup definition → MVP → this post.
CAC (Customer Acquisition Cost)
CAC = Sales & marketing spend in period / New customers in period
Include: ads, salaries for GTM, tools, events — allocated to acquisition.
Exclude: product development (usually).
Early-stage warning: CAC looks amazing when founders do all sales manually. It explodes when you hire — model both.
LTV (Lifetime Value)
Rough SaaS formula:
LTV ≈ (ARPU × Gross margin %) / Monthly churn rate
Or simpler early on: average revenue per customer × average months retained.
If churn is unknown, use cohort data from first 90 days — don't assume 5% monthly because a blog said so.
The Golden Rules
| Rule of thumb | Meaning |
|---|---|
| LTV > 3× CAC | Healthy SaaS target (varies by stage) |
| Payback < 12 months | Cash-efficient growth |
| LTV:CAC < 1 | You lose money on every customer — fix before scaling |
Violating these while raising burn is how runway dies quietly.
Improving Unit Economics
- Retention — fix product before ad spend (problem-solution fit)
- Pricing — Revenue research mindset; first price often too low
- Channel — organic and PLG beat paid for early B2B vs B2C
- Scope — fewer customers, higher value beats vanity logos
Revenue research thinking in Unicorn Rivals mirrors margin and MRR tradeoffs.
What Investors Ask
- CAC by channel
- Payback period trend
- NRR / expansion (later stage)
- Gross margin after support load
At pre-seed, honest cohort charts beat fantasy LTV spreadsheets.
Related reading
Practice economics under rivalry
Unicorn Rivals — customers, MRR, and five resources on a shared leaderboard.
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