If that is the case, then it means we are hiring H-1B workers who are less skilled on average, than the average US worker. If H-1Bs weren't available, companie

If that is the case, then it means we are hiring H-1B workers who are less skilled on average, than the average US worker. If H-1Bs weren't available, companies would be forced to keep raising the offered salary when they couldn't fill a position. Virtually any position can be filled given a high enough salary. Therefore if companies are choosing to hire H-1Bs instead of raising the salary to the level necessary to fill positions with US workers, then it is because it is cheaper to pay the H-1B costs.