>For most companies and applications, developer time is many orders of magnitude more expensive than machine time. For me the context was mostly working in Dev

>For most companies and applications, developer time is many orders of magnitude more expensive than machine time. For me the context was mostly working in DevOps CI/CD. Slow CI scripts slow down developer feedback and cost machine time as well as developer time. If your customers are your developers, performance engineering is about saving the expensive developer time. And if you ask me the effects are non-linear, too. If your build system takes 1 minute or 10 minutes for a diff build the time lost won't be a mere factor of 10. Any sufficiently long time and your developers will lose focus and their mental model, will start making a coffee, and maybe they might come back later to that work after 3 meetings that got scheduled in between.