I have been looking at this as well in my practice. I am a newbie and i don't have any clients just yet but this is the way I point out my reasoning to pay $25 per hour vs $10 for a part-time employee.
- There is no "overtime"
- My clients may pay a little more for my services than a p-t employee, but I can do the work of a full time staff member for a little more than p-t pay (when factoring in overhead and extras)
Like I said, I have no clients yet, but those potentials I have spoken with are interested after I break it down like that