One of the process is called the LCA (Labor Condition Application). Employer needs to tell the government how much they are paying this new foreign worker. And the gov decides if the wage is at least equal or higher than if you were to hire a US national for the same position.
See, if you are allowed to pay the foreigner less, then hiring US citizens would be disadvantageous... LCA protects the citizens (and on the book protect the foreigner from exploitation lol) (5/12)