It is an upper bound essentially for a sustainable company and is a point of convergence "your salary <= your value add". It actually maxing out implies being done only because all supply is accounted for. A bigger "value add - salary" essentially moves towards the front of the queue for hiring.

If given two "equal" canidates why pay more if you don't have to? (The actual equality given other complications like cultural, language barriers, and similiar is another topic.)

The "fairness" is also not mathematically viable as it assumes axiomatically that no action can be taken to earn profit that isn't "unfair" as the deserved value is based upon output and not input provided, which leaves no room for expansion nor buffer and no incentive to actually operate a business.

TL;DR - most popular understanding of economics is pretty damn confused.

I'm sorry, but I did not understand your comment at all. Some of those sentences don't parse for me. I don't know what you're trying to say. Can you please clarify?

It seemed clear enough to me. Your salary is less than or equal to the value you add (companies will usually not knowingly pay you more than you’re worth), not equal to it.

The rest was expanding on that core point by computing the expected profit a company gains by hiring someone (value - salary [minus total costs, actually]) and that a company will seek to maximize its profits.

I guess I was confused by the use of the pronoun "it" right at the beginning. With no context, I had trouble deciding what it mean, or deciphering much of the post. What you explained is the only bit I was able to guess at on my own, mostly because it's common sense.

The part about the mathematical viability of fairness was particularly quite puzzling.

I read the initial it as “your salary = your value add” giving a single point figure which is the upper bound of the inequality “your salary <= your value add” and the upper bound on what a sound company would pay.

(It’s actually higher than what a sound company would pay, but if you switch salary out for “total cost to company”, it becomes correct again.)