How much should I charge for tutoring?
Response: "How much do you want to charge?"
There are no guidelines or rules on what tutors should charge. For each person who thinks your rates are expensive, there'll be a person who'll think you are cheap!
You have to decide what your time is worth. Take into consideration travel time, tracking down resources, research, review and preparation time, materials, advertising and promotion, permit/licence/insurance costs, your background educational costs and perhaps more that I haven't thought of. Factor in your costs and actual time devoted to tutoring one student, and obviously your per hour rate is covering much more than the one hour with the student.
You may want to start off with a cheaper rate in hopes of getting more students, but then some may perceive a higher rate with a higher quality tutor.
If you are still wondering if you are charging an appropriate amount for tutoring, you could try looking at a list of tutors that cover the same subject as you. You shouldn't feel obligated to follow the "average" though, remember that they have all decided on their own rate as well, and only represent a small portion of tutoring and private education options available to students and parents. If you feel you are worth more, certainly ask for more, if you feel you could still make a reasonable income by charging less, then that's your choice too.