It's nearly impossible to measure the marginal contribution of someone one in a non sales role.
It certainly wouldn't benefit anyone who hires people if those people could estimate their own contribution, or, god forbid, compare it to their compensation. I think there's a term for the difference which now eludes me.
The floor is mostly arbitrary (see the wage collusion scandal between Apple and Google for an example), and then beyond that it's a question of who is the most productive, effective at getting things done, etc.
So while they do have "something to measure," these metrics can be uncorrelated with profitability - or even negatively correlated with it. It's possible for a productive team to spend their time on an unprofitable project, while another team barely works but ships a profitable product.