What percentage of the per-employee revenue do employees deserve? Negotiation is the way of establishing this, and 'value' is only one part of the equation.
Similarly: price of products on the market are not established based on how valuable that product is to the buyer. That's only one factor.
I understand the appeeal of what you're saying, but we don't have many good examples of it working well.
While this may vary from company to company and even job to job surely all employees doing the same job deserve the same per cent.
You wouldn't give one salesman twice the commission because he's a 'superstar'
I have started believing in unions more over the years because I work for a company that is well known for doing the right thing and caring. Yet, I've repeatedly seen the company break its own policies and screws people over. So I feel the issue is pervasive if this is really a "good" company.
It could be that contracts without a union could fix my main complaint - not consistently following the rules. But the only way to force this is through legislation or unions. Unions seem to be more feasible.
But it's funny, because a lot of left parties here (even the ones with the red star in the logo) are always saying that we should tax work less, and tax capital gains more... but then the "other party" does that, and they start protesting (probably because they hope to be in the government after the elections, and want the money to steal for themselves).
Basically, the only solution for our government is to take them on a vacation with a plane somewhere, like with the polish politicians - https://en.wikipedia.org/wiki/Smolensk_air_disaster
In the US, for years the corruption was organized crime controlling the labor unions to extract money for themselves mostly through "protection" from them starting strikes.
The status of my salary has an easily articulated and understandable explanation. Nobody did anything wrong and nothing needs to be done to correct it (by anyone but me).
I recognize, for what it's worth, that this is not a popular intuition (even though I maintain that it's the correct one). People get similarly outraged when they learn about price discrimination schemes, which I find entirely unobjectionable.
Your example of products being purchased is a completely different paradigm due to many reasons. The consumer information is available to the company through many avenues such as market research and affiliates. The company generally conceals the cost of producing an item. The scope and duration of the transactions are also majorly different. Let's also remember that the price for the object is the same for everyone, yet you are offering different pay for the same value to the company. That's the problem.
If we really want to go full capitalist libertarian and let markets decide everything, then let's do away with all the protections. I don't want to live half in one system and half in another. Why should we have protected classes or offer accommodations for disabilities? I think you'll find the answer also supports other workers rights, such as the ones being discussed/proposed here.
I disagree with the language you use later in the comment (fought, won, given). Negotiation skills shouldn't drive compensation. Value to the company should. If someone is doing the same work and making the same value, then they are earning their salary. Differences in pay can be explained by documenting the difference in value that is produced - something they should already be doing in performance reviews.
These steps could help anyone negotiate. I'm not a woman and I was lowballed out of college due to a market downturn at the time and my salary has suffered ever since.