I worked for an employer once who considered doing this for different reasons. He decided not to after realizing that the full-timers and the temps would get to talking to one another and that the full-timers would quickly figure out that he was paying the temp agency about double per hour what they were making.
“He decided not to after realizing that the full-timers and the temps would get to talking to one another and that the full-timers would quickly figure out that he was paying the temp agency about double per hour what they were making.”
In this time of falling wages, that probably wouldn’t be a problem anymore. Pay both the employees and temp agency $15 an hour (and in the end the temp will make $12); the days where a temp for a $15/hour position costs $18/hour are over.