A junior developer costs $40,000 per year. A senior engineer costs $120,000. The junior is a bargain, right?
Wrong. Here is the math nobody shows you.
The real cost of a junior developer
Let us say you hire a junior at $40K/year. Here is what happens:
- **Month 1-3:** They need onboarding. A senior engineer spends 40% of their time mentoring instead of building. Cost: ~$12,000 in lost senior productivity.
- **Month 4-6:** They start contributing at 30% of a senior's output. Their code needs heavy review. Cost of review time: ~$8,000.
- **Month 7-12:** They hit 50% productivity. Code quality improves but still needs oversight.
- **Year 2:** Many leave for higher-paying roles. You start over.
Total real cost of a junior in year one: ~$60,000-80,000 in salary + lost productivity. And the code they wrote in months 1-6? Most of it needs rewriting.
What a senior engineer actually delivers
A senior engineer at $120K/year:
- Ships production code from week one
- Needs zero hand-holding
- Makes architecture decisions that last years, not months
- Pushes back on bad ideas before they waste budget
- Mentors juniors as a force multiplier, not a productivity drain
The hidden cost multiplier
The biggest cost is not salary. It is the code that needs rewriting six months later. Every hour of junior code without proper review creates 3-5 hours of future remediation work. Multiply that across a codebase and you are looking at hundreds of thousands in technical debt.
When juniors make sense
Junior developers are not bad hires. They make sense when:
- You have a strong senior team to mentor them
- You are building for the long term
- You accept lower short-term velocity for long-term team building
But if you need to ship a product in 8 weeks and every dollar counts, hire the senior. The math is not even close.