It depends on where you are? If you live in an area that is depressed, you may be surprised what 15$ an hour gets you? In my area, I know guys and gals with PHD's and other degrees working at grocery store for a 1$ an hour over minimum wage.
It is also relevant to the person you hire. If they are single with no real responsibilities? 15$ may be a great wage. If they have a wife and 2 kids, it won't even pay the grocery bill, Lol