I suggest you sell yourself (your work) as expensive as you can. But keep in mind that employers have to keep all employees satisfied.
In some organizations there are clear rules who gets how much depending on their education (which documents can they provide) the position and the time they are working in that organization. Everybody knows their position in that pecking order and they (have to) accept it. Such an organization is normally not attractive for better than average people.
But even in more flexible companies the management has to make sure they keep everybody reasonably happy. Let's say they would give you 50% more salary then others because they think you are very good. And lets say you do a very good job and they would give you even more because they know you are good.
Consider what will happen when other people find out that you get so much more than they get. Some will understand that you are better and you earn more. But there will be others who won't like it at all when you get more. Especially if these people think you are not so much better and if they are longer in the company then you.
What will the boss do if these people complain? Obviously he can tell them accept it and that's it. But this will be bad for their motivation. So the boss needs to balance what he does. If he is too good to you the others won't like it. If he is not good enough to you then you won't work there.
Maybe the boss would be willing to give you more but he can't handle problems with the others.
Maybe you can make a deal that you get a "normal" salary and a big bonus which the others don't have to know about. But depending on the company it may be difficult to hide such a deal.
Edit: After all the comments I like to add: What I describe here is not the way I think things should be but the way they are. Personally, I negotiated often enough the payment I wanted (mostly freelance work). I work mostly for small companies and I talk directly with the boss and that is confidential between him and me. But in bigger companies other people will know and sometimes this information can’t be kept secret. And then, if the lower paid people find out and get upset, this can be a huge problem for the whole company. Smart bosses avoid getting in this kind of trouble. What the lower paid people do is human nature. I cannot change it.