Shortages always exist at a given price. If people demand their iphones cost only $100, there would be a massive shortage of iphones.
Same goes for labor: if you pay shit, demand for that job is going to be shit.
Of course on the labor side, part of the "price" is job satisfaction, working conditions, etc. Many more people would rather be receptionists at $17/hr than working in a warehouse or factory for the same rate.