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Your most expensive engineer is going to send a resignation email in October.
You will read it and feel ambushed. He just got promoted. His comp is at market. His one-on-ones with you have been fine. Two of his teammates complimented his work in the last all-hands. The note will say he's leaving for "an opportunity to build something new," and you will spend the rest of the morning trying to remember when he stopped sounding like himself.
The chain of decisions that produced this resignation began with a budget you closed last September, when you decided to skip the junior hire.
What the senior+AI math looked like nine months ago
You ran the numbers and they were clean. A senior engineer with the Cursor and Copilot and Claude subscriptions you'd already approved could ship more than a two-person team from 2023. Your internal benchmarks pointed that way. Your CTO did too. The thread in your founder Slack ran with it, posting a chart from McKinsey's developer survey showing a 46% reduction in time on routine coding tasks.
The senior cost $220K all-in. Adding a junior would have run another $130K. With AI subscriptions at $400 a month, the math came down to a $225K-versus-$350K choice. That's a Series A burn rate problem solved with one calendar invite, and your CFO sent a thumbs up.
The hire you skipped never showed up on any dashboard. Most decisions that cost a company a year of velocity hide that way. The line item gets cut from the budget. The role never gets opened. The cost shows up two summers later, in a one-line resignation note.
