Unit Economics

Unit Economics

Growth without positive unit economics is accelerated insolvency. Marketing and growth investments must be governed by fully-loaded Customer Acquisition Cost (CAC), gross-margin-adjusted Lifetime Value (LTV), cash payback velocity, and channel-level contribution margins.

1. Core Mathematical Formulations

A. Customer Acquisition Cost (CAC)

Distinguish between blended and paid acquisition costs:

• Paid CAC: $$\text{Paid CAC} = \frac{\text{Direct Paid Ad Spend}}{\text{Customers Acquired via Paid Channels}}$$
• Fully-Loaded CAC (the true economic floor): $$\text{Fully-Loaded CAC} = \frac{\text{Ad Spend} + \text{Agency/Creative Fees} + \text{Salaries (Sales + Mktg)} + \text{Software Stack}}{\text{Total New Customers Acquired}}$$ Rule: Always use Fully-Loaded CAC when setting budget ceilings.

B. Customer Lifetime Value (LTV)

Never calculate LTV using top-line revenue alone; LTV must be adjusted for cost of goods sold (COGS): $$\text{LTV} = \frac{\text{ARPU} \times \text{Gross Margin %}}{\text{Customer Churn Rate (Monthly)}}$$

• ARPU: Average Revenue Per User/Account per month.
• Gross Margin %: (Revenue - Hosting/Payment/Support COGS) / Revenue. For B2B SaaS, benchmark is 75%–85%; for e-commerce, 40%–60%.
• Expansion-Adjusted LTV (when Net Revenue Retention > 100%): $$\text{LTV} = \frac{\text{Initial ARPU} \times \text{Gross Margin %}}{\text{Churn Rate} - \text{Expansion Rate}}$$

C. CAC Payback Period (Cash Velocity)

Payback measures how many months of gross profit are required to recover the cash spent to acquire a customer: $$\text{CAC Payback (Months)} = \frac{\text{Fully-Loaded CAC}}{\text{Monthly ARPU} \times \text{Gross Margin %}}$$

D. Channel Contribution Margin & Break-Even ROAS

Determine whether an individual acquisition channel is accretive: $$\text{Contribution Margin} = \text{Attributed Net Revenue} - \text{COGS} - \text{Channel Ad Spend} - \text{Payment Gateway Fees}$$ $$\text{Break-Even ROAS} = \frac{1}{\text{Gross Margin %}}$$ Example: At 70% Gross Margin, break-even ROAS is 1 / 0.70 = 1.43x. Any campaign below 1.43x ROAS destroys cash on the first transaction.

2. Benchmark Health Scorecard

3. Worked Example: B2B SaaS Tier

Given:

• Monthly subscription: $200/month
• Gross Margin: 80% (Hosting + payment processing = $40/month)
• Monthly customer logo churn: 2.5% (Average lifetime = 1 / 0.025 = 40 months)
• Total sales & marketing monthly spend: $40,000
• New customers closed per month: 25

Calculations:

1. Fully-Loaded CAC: $40,000 / 25 = $1,600
2. Gross Margin ARPU: $200 * 0.80 = $160/month
3. LTV: $160 / 0.025 = $6,400
4. LTV : CAC: $6,400 / $1,600 = 4.0x (Healthy scaling zone)
5. CAC Payback: $1,600 / $160 = 10 months (Meets the <12 month B2B benchmark)

Critical Rules

1. Never report Blended CAC as an excuse for an unprofitable paid ad channel; paid campaigns must stand on their own Paid CAC.
2. Always deduct variable delivery and payment processing costs from revenue before computing LTV.
3. If churn exceeds 5% monthly, fix customer retention and onboarding before increasing acquisition spend.

Verification Checklist

• CAC calculation includes fully-loaded personnel, agency, and tooling costs.
• LTV uses gross margin dollars rather than gross revenue.
• Payback period calculated against gross profit contribution per month.
• Break-even ROAS and contribution margin calculated for each paid channel.
• Baseline metrics compared against industry cohort benchmarks.

Anti-Patterns

• NEVER use a single company-wide LTV across disparate customer segments (e.g. self-serve vs enterprise).
• NEVER assume lifetime is infinite when churn is low; cap lifetime at 36 or 60 months in financial models.
• NEVER scale marketing budgets based on top-line revenue when net contribution margin is negative.