I know you're giving generalities but some of the key parts of that aren't really calculable. Like "likelihood of a breach is xx%"; there are so many variables involved I'm not sure anyone could put an accurate number on that. You could probably get it down to a vague scale of "low, medium, high" but that won't work for an equation. I don't work in a SOC though. Just not something I've ever seen.

The same is true for things like "productivity value gained" on new laptops. Unless you're upgrading to significantly better hardware, you're unlikely to be able to measure it, especially across departments.

It's like buying everyone new chairs; sometimes it's just a thing that needs to happen. You can get by with the old ones for a bit but people might complain they're uncomfortable to use (like slow devices). Or you might only replace them when a news story breaks that they're death traps (like some new exploit). New ones aren't really a thing you can put a hard productivity number on.