How do you all quantify the revenue impact of your work product?

I'm (mostly) an academic so pardon my cluelessness.

A lot of the advice given on here as to how to write an effective resume for industry roles revolves around quantifying the revenue impact of the projects you and your team undertook in your current role. In that, it is not enough to simply discuss technical impact (increased accuracy of predictions, improved quality of data etc) but the impact a project had on a firm's bottom line.

But it seems to me that quantifying the *causal* impact of an ML system, or some other standard data science project, is itself a data science project. In fact, one could hire a data scientist (or economist) whose sole job is to audit the effectiveness of data science projects in a firm. I bet you aren't running diff-in-diffs or estimating production functions, to actually ascertain revenue impact. So how are you guys figuring it out?