Hot-ish take incoming:

It's even less complicated than all this. You spend X on a feature to increase revenue by Y. You pay a plumber N so you don't have to pay a flooring guy 10N. In some orgs, if they're large, you could replace $ with $KPI, but $KPI should still be obviously quantifiable. If you're an engineer without obviously quantifiable KPIs (especially if you're a young-ish engineer with ambitions of becoming really excellent one day), you might consider selling your skills to a more serious employer.