If you can't live well on $25/hr you're a tool. I guess you must think school teachers making $15/hr aren't worth as much as you because you can... what, rig a light? Get real.
Except that that $15/hour teaching job isn't the same as a grip's $25/hour job. A teacher is paid for an 8-10 hours day, almost every day. A grip is paid for the duration of the shoot, and that might only take a day or a few days out of the week. When you're not fully booked all the time, you have to charge more.