You pay the asking price if the product provides you enough value. Negotiation is simply setting the asking price, which is absurdly mundane in a free market economy. In fact, not setting an asking price - thus letting the buyer decide what he pays - contradicts norms.

The metric of “how well you do your job” is highly subjective anyhow; between an employee, their manager, their product manager, their coworkers and HR there would be significant variance of opinion.

1. Negotiating skill is a skill as any other soft skill.

2. If somebody consider that he doing the same job (have the same skill) it doesn't mean that it's true.

If negotiation is not a skill that affects your job performance it seems unfair that it has such a big influence on your pay.

That’s how sales work unfortunately