>no way to figure out how much each person is actually worth //
You're not buying a person though. In employer terms you're usually buying the completion of a particularly series of actions. These actions can be analysed and given a money value.
Neither employers nor employees have incentive to give a fair value in one of the directions. I'm sure there are plenty of overpayed employees that aren't exactly falling over themselves to get a pay cut, nor companies falling over themselves to give employees a pay raise.
You're not buying a person though. In employer terms you're usually buying the completion of a particularly series of actions. These actions can be analysed and given a money value.