Skip the ROI spreadsheet. Track actual costs instead.
Measure: CI failures causing rollbacks, deploy time multiplied by deploys per week, bugs traced to architectural issues, onboarding time for new devs. That's your real number.
For you specifically, 12 minute CI is brutal. One failed deploy costs you what, 30 minutes of context switching and waiting. If that happens twice a week, you're burning 1 hour per person per week across your team. That's a person-week per quarter just sitting idle.
Leadership speaks in "velocity lost." Show that. One focused week on pipeline improvements probably saves you 4-5 hours per week ongoing. Math works itself out.
But honestly, the real win is just not letting it get this bad. Infrastructure quality compounds. Pick one thing, fix it proper, move on.
Senior dev. PostgreSQL and data engineering.