A $20,000 Workflow? Analyzing React Native's CI/CD Costs
While developing BuildBudget (currently in beta), a tool for analyzing GitHub Actions costs, I discovered something surprising: the most expensive workflow among the top 10 GitHub organizations wasn't in a machine learning repository training models on GPUs, nor in a complex monorepo building thousands of packages. It was React Native's "Test all" workflow, costing nearly $20,000 per month – with individual runs averaging $35.37, about 80 times more expensive than the typical GitHub Actions workflow. You can explore all results yourself at buildbudget.dev/demo.
These numbers come from analyzing 562 workflow runs, with the vast majority triggered by pull requests. But what makes this workflow so expensive?
The most expensive jobs in the workflow are iOS tests, costing up to $3.86 per run. While GitHub provides free standard runners (ubuntu-latest) for public repositories, specialized runners like macos-13-large still incur costs – about 10x more than standard Linux runners. What's interesting is that these expensive jobs have relatively low execution rates (5.9%), suggesting the team is already trying to minimize their usage.
The workflow makes extensive use of matrix strategies, which can dramatically increase costs. Take the iOS tests above – they run variations across:
