In the area that I teach, most of the licensed teachers are charging $50-70/hour. Some of the lower elementary only charge $40/hr, and the high school math, science, and foreign language teachers charge $75+ per hour. This is the Northern Virginia area (Fairfax, McLean, DC). When I started charging $50/hr, I was told that my rates were very low for my qualifications.
I have taught in a few different areas, and tutors rates quite often correspond with their skills. The really good tutors do charge more. You get what you pay for. One thing is knowing the subject matter, and another is knowing how to teach. That being said, there are some great college (and even high school students) who are good at tutoring. They are few and far between, but there definitely are some out there, and the rates would be closer to $20-25/hr if you go privately. When people go through agencies they pay a lot more than that and generally get someone with no qualifications or who have strengths NOT in the area they are tutoring (for example, college English majors tutoring math).