If you were theoretically willing to pay $5 for a gallon of milk and you walked into a store and they were selling it for $2, I'm sure you wouldn't insist they take the extra money. It's the store's job to figure out how much to charge for milk. It's your job to figure out how much you're willing to charge for your labor.
You could argue there's an important caveat of symmetric information around this interaction if you want to talk about fairness. Asymmetric information is frequently considered an unfair advantage (see insider trading) but is also recognized as the source of much profit (see auction winner's fallacy), but you have to at least recognize that employers by and large have a huge information advantage in the labor market currently.
It's true that employers are privy to a lot more salary information than employees. I know I said what other people are paid is irrelevant, which I think it is in terms of fairness, but you should be (and, legally at least, in the US, are) free to take that information into account when deciding what you'll accept. It's still up to you to make that decision and hold employers to it. They aren't going to offer up higher salaries out of the kindness of their heart or some sentimentality about fairness.
Unfortunately that's not quite true. Milk (and other foodstuffs) are a requirement to live. People are "willing" to pay more for that because they don't really have many other options. So it's ripe for abuse.
Salary negotiations are not fraud. Fraud involves being promised something and not getting what you agree to.
If someone says they’ll give you X in exchange for Y and then they do exactly that, that isn’t fraud.
I’m not sure you understand what the word fraud means.
Well there's 2 major theories of thought about that.
One is that the holders of the capital decide how much to pay, and they make the bulk of the market. You get paid what you negotiate.
The other is that the worker will never be paid what they are worth. In other words, their surplus value is equal to the new value created by workers in excess of their own labor-cost, which is appropriated by the capitalist as profit when products are sold.
And in this country, we're seeing the beginning of the second with Antiwork and the Great Resignation. Many of us Zennials are really tired.
What's unfortunate is that people aren't willing to see the change go downward ever and then also argue that others can't go upward because... well then you yourself "can't" go upward.
What's deserved is for people to be compensated fairly. If the company is compensating someone unfairly and can't compensate someone fairly because of then, then that is a definite and clear problem.
Whatever your definition of fair is, whether that's "deserving" or "market forces", it's still the same argument.