06 · Topic
Profitable businesses run out of cash all the time.
Key numbers
Unit economics: the only four numbers that matter
Gross margin
Revenue minus the direct cost of delivering it. For software, gross margin sits at 70 to 85%. The cost of one more customer is mostly hosting and support. For a coffee shop, it is 65 to 75%: the cost of beans, milk, and a paper cup. For a hardware company, it is 35 to 55%. Gross margin caps the entire business; nothing you do downstream beats it.
Contribution margin
Gross margin minus the variable cost of acquiring and serving the customer (sales commissions, payment processing, customer support time). Contribution margin tells you whether each new customer actually adds to the pile of cash. A business with great gross margins but a sales team that takes 80% of new revenue as commission has weak contribution margins, and growth burns cash.
CAC (Customer Acquisition Cost)
Total sales and marketing spend in a period, divided by new customers acquired in that period. Modern direct-to-consumer businesses live and die on CAC. A jewelry brand spending $40 on Meta ads to acquire a customer who orders one $90 product is in a different business than one paying $200 to acquire a customer who orders three $90 products a year for two years.
LTV (Lifetime Value)
The total contribution margin a customer generates before they churn. Crudely: LTV ≈ ARPU × gross margin / churn rate. A $50/month subscription with 80% gross margin and 4% monthly churn has an LTV of about $1,000. The ratio that matters is LTV / CAC. Investors look for 3.0× or higher. Below 1.0 means you lose money on each customer you acquire.
CAC payback period
Months it takes for the contribution margin from a customer to recover the cost of acquiring them. Healthy SaaS: 12–18 months. The longer your payback, the more growth capital you need to fund the gap.
Pricing: what you charge is what you are
Most first-time founders price by guessing what is competitive and slipping a little under. That decision compounds. Pricing too low leaves money on the table. It also determines which customers you attract (price-sensitive, demanding, churn-prone) and which features you can afford to build.
Cost-plus vs value-based
Cost-plus: add a markup to what it cost you to produce the thing. Standard in retail and contracting. The ceiling is the next competitor's price.
Value-based: charge what the buyer saves or earns from using the product. A piece of software that saves a customer $50,000 in manual data entry can be priced at $5,000–$10,000 a year. The ceiling is the value created, not the cost to build.
Most B2B businesses leave money on the table by sliding toward cost-plus when buyers would have paid value-based prices. The question to ask in pricing calls is: “What was this problem costing you before?” The answer anchors the conversation.
Cash flow vs profit: the trap that kills
A standard founder failure: the P&L looks great, the bank account is empty.
Take a B2B company adding 6 customers a month at $80/month. Most sign annual contracts; 40% of revenue is collected as annual prepay (later), 60% as monthly. CAC is $800 per customer. Headcount opex is $18k/month and growing. Starting cash: $80,000.
Profit climbs above -$286,056. Cash crosses zero by month 12 and ends at -$324,712. Both are real numbers. Only one of them gets the founder to next year.
The solution to this specific problem is either to demand annual prepay (kills the cash gap) or to raise enough capital to fund the working capital cycle. The general lesson: track the cash chart, not the income statement, every Monday morning.
The 3-statement model, minimum viable
Three reports tell you what the business is.
- Income statement (P&L): revenue, costs, and profit over a period. Tells you whether the business model works.
- Balance sheet: snapshot of assets, liabilities, equity at one moment. Tells you what the business owns and owes.
- Cash flow statement: changes in cash from operations, investing, financing. Tells you whether you survive to next quarter.
They are linked. Net income flows into retained earnings on the balance sheet. Cash flow reconciles accrual profit back to actual cash. A founder who can read all three in 5 minutes makes faster, better decisions than one who only sees revenue.
Why most small businesses fail
The cited statistic, 80% of small businesses fail in 18 months, is roughly the right order of magnitude but is overstated by counting any closure as a failure. Even discounting that, the dominant causes of real failure are not what most founders fear:
- Ran out of cash (38% of failures cited in CB Insights post-mortems). Usually because growth outpaced funding, or because revenue forecasts assumed a sales cycle that never materialized.
- No market need (35%). The product was real, the team was real, the customers were not.
- Got outcompeted (20%). Often because a competitor chose a better pricing model or a better distribution channel.
- Team problems (18%). Co-founder fights, wrong early hires, founder burnout.
The remedy for cause 1 is cash discipline. The remedy for cause 2 is talking to customers before building. The remedy for cause 3 is finding a real differentiator early. The remedy for cause 4 is choosing a co-founder the way you would choose a spouse.
Revenue is vanity. Profit is sanity. Cash is reality.
Common mistakes
- 01Pricing on cost-plus instead of value-based. A 50% margin on a $4 product is $2. A 50% margin on a $400 product is $200. Same multiplier; vastly different business.
- 02Ignoring LTV/CAC ratio. A profitable customer who costs $1,000 to acquire and is worth $1,200 over their lifetime is a worse business than one with a $50 CAC and $500 LTV. Same gross margin; very different growth math.
- 03Hiring before product-market fit. The single largest reason early startups fail is burning cash on a team to build features that do not move conversion. PMF is a survey response, not a hiring milestone.
- 04Confusing revenue with bookings. A signed annual contract for $120k is a booking. If the customer pays monthly, only $10k is revenue in month one. Burn against bookings is how you die with a full pipeline.
- 05Building a business around being available. If the business stops earning when you sleep, you have bought yourself a job, not built an asset.
FAQ
What is a good LTV/CAC ratio?+
Investors look for 3.0× or higher, meaning a customer is worth at least three times what it costs to acquire them. A ratio below 1.0 means you lose money on every customer you bring in.
Can a profitable business really run out of cash?+
Yes, and it happens often. Profit is an accounting figure that can include revenue you have booked but not yet collected. If customers pay you slowly while you pay your costs now, the bank account empties even as the income statement looks healthy.
What is the difference between cost-plus and value-based pricing?+
Cost-plus adds a markup to what the product cost you to make, so the ceiling is the next competitor's price. Value-based pricing charges a fraction of what the buyer saves or earns, so software that saves a customer $50,000 can be priced at $5,000 to $10,000 a year.
What is the most common reason startups fail?+
Running out of cash is cited in 38% of CB Insights post-mortems, usually because growth outpaced funding. The next most common cause is building something with no market need, at 35%.
Further reading
The Lean Startup
by Eric Ries
Build–measure–learn. The methodology is more useful than the manifesto chapters. Skip the case studies; read the chapters on validated learning.
Profit First
by Mike Michalowicz
An aggressive cash management system for small business. The percentages he recommends are too rigid, but the principle, pay yourself before paying expenses, is the right reflex.
Zero to One
by Peter Thiel
The chapter on monopolies versus competition reframes how to think about pricing power. The rest is more polemical than useful.