Customer Acquisition Cost (CAC) vs. LTV

In Silicon Valley, we don't just ask "Are we profitable?" We ask "Are our Unit Economics healthy?" This means: does it make sense to buy more customers?

The Two Big Numbers

1. CAC (Customer Acquisition Cost): The total cost of sales and marketing divided by the number of new customers.
2. LTV (Lifetime Value): The total revenue you expect to get from a customer before they cancel.

The "Magic Ratio"

Investors look for an LTV/CAC ratio of 3:1 or higher.

• If it's 1:1, you are spending all your profit just to get the customer. You will go bankrupt.
• If it's 5:1, you are very efficient and should spend more on marketing to grow faster.

Talking about Efficiency

• "Our CAC is too high on Facebook; let's try LinkedIn."
• "We can increase LTV by improving our retention."
• "What's the payback period on our latest campaign?"

Alex's Tip: If you are in a product meeting, and someone suggests a feature that "reduces churn," they are really saying "I want to increase our LTV." Use the financial term to sound more strategic!

• NRR below 100% means you are losing revenue from existing customers overall.
• NRR of 100% means revenue from existing customers is flat.
• NRR above 100% means existing customers are spending more over time, even after churn.

An NRR above 100% is the holy grail of SaaS. It means the business can grow even without acquiring a single new customer, because existing ones expand. Top SaaS companies like Snowflake have reported NRR above 130%.

Why retention beats acquisition

Acquiring a new customer is expensive (the CAC). Keeping an existing one is usually much cheaper. When churn is high, the company must spend constantly on acquisition just to stand still.

A useful image: imagine a bucket with a hole. Pouring more water in (acquisition) does not help if the hole (churn) is large. Fixing the hole (retention) is often the higher-leverage move.

This is why SaaS teams obsess over reducing churn. Even a small reduction in monthly churn dramatically increases LTV over time.

Common mistakes

1. Reporting only gross churn. Net churn (or NRR) tells the real story, because upgrades offset losses.
2. Confusing logo churn with revenue churn. Losing one big enterprise customer can outweigh ten small ones.
3. Celebrating new signups while ignoring churn. Net growth is what matters, not gross signups.

Practice

A company starts the month with $100,000 in recurring revenue. It loses $3,000 to churned customers, but existing customers upgrade by $8,000.

1. What is the gross revenue churn?
2. What is the NRR?

Answers:

1. Gross churn = $3,000 / $100,000 = 3%.
2. NRR = ($100,000 minus $3,000 + $8,000) / $100,000 = $105,000 / $100,000 = 105%. Existing customers grew revenue by 5%, even with some churn.

In the next lesson, you will learn pricing models, how SaaS companies decide what to charge.