Unit economics and finance
Income statement lines
Revenue minus COGS is gross profit. Minus S&M, R&D and G&A is operating income. Headcount dominates the opex lines.
The P&L (profit and loss statement), also called the income statement, answers: over this period, what did we earn, what did it cost to deliver, what did we spend to operate, and what was left? It is not the bank balance. That is the cash flow statement.
Revenue
− COGS
= Gross profit
− Sales & Marketing (S&M)
− Research & Development (R&D)
− General & Administrative (G&A)
= Operating income
± Other income / expense
− Interest
− Taxes
= Net incomeWalking through the buckets
Revenue on a SaaS P&L is what you earn in the period, not what you collected. ARR and MRR are operating metrics, not GAAP lines. A company can have $5M ARR and much less than $5M of recognized revenue in a year if it is growing fast and ramping mid-year.
COGS is the first subtraction. Gross profit / revenue = gross margin.
Three opex buckets dominate startups:
| Bucket | What it is | Typical early-stage role |
|---|---|---|
| S&M | Sales reps, marketing, demand gen, tools, travel | Often the largest cash consumer when scaling |
| R&D | Product, engineering, design, research | The product factory |
| G&A | Finance, legal, HR, facilities, executives not in S&M/R&D | Should stay lean longest |
Headcount is the biggest cost. A fully loaded engineer in a US hub might be ~$200–280k all-in (salary, benefits, taxes, equipment, tools) as of 2025–2026 orders of magnitude. A quota-carrying AE can be similar or higher with OTE. Ten unexpected hires are a seven-figure annual opex decision.
When someone says "we only hired two people," translate: 2 × $250k = $500k / year ≈ $42k / month of burn before they produce anything.
A 12-person eng org at $22k fully loaded each is ~$264k/month ≈ $3.2M/year.
Common mistakes
- Treating Stripe cash as revenue in investor updates.
- Putting founder "sweat" at $0 while comparing margins to peers who pay market salaries.
- Booking one-time professional services as recurring revenue without calling it out.
Check yourself
- Two hires at $250k fully loaded. What did you just add? About $500k/year, or $42k/month, of opex.
- Ending ARR is $5M and the company grew all year. Is recognized revenue $5M? Usually less — average ARR over the year was lower than ending ARR.
Key takeaways
- The P&L flows Revenue → Gross profit → Operating income → Net income.
- Opex is mostly S&M, R&D and G&A. Headcount dominates all three.
- Revenue ≠ cash collected. ARR is not a GAAP line.
- Translate "we hired two people" into annual dollars before you celebrate.
Further learning
Why January cash is not January revenue: revenue recognition.
Related
The P&L for startups
Reading and building an income statement — revenue recognition, COGS, S&M / R&D / G&A, EBITDA and net income — with a worked $5M ARR SaaS example.
COGS vs opex
COGS is the cost of delivering the product to customers. Opex is the cost of building and running the company.
Cash flow and the three statements
Why profit ≠ cash, how the balance sheet and cash flow statement work, deferred revenue from annual prepay, and how the three statements link.