The number of classroom hours and the expense of materials supplied should be the deciding factors for how much to charge. I think it is best if the student learns on her own machine, and uses her own supplies for the most part (rulers, mats, rotary cutters, etc.) with the teacher possibly supplying iron and ironing board. For semi-private lessons I would expect to pay more than for larger group lessons. I would also expect to pay more for a nationally recognized teacher with lots of teaching experience. Other than that, I think it comes down to how much people in your area are willing to pay and how much you need to charge to make it worthwhile to you.