Hello!
I too have had this question, as I started to charge for my readings and reiki about a year and a half ago. I was in the same situation...feeling that if I charge too much, maybe I was going too high, but charging too low made it seem I wasn't competent enough.
I have been to many readers in my area over the years, some are "a dollar a minute" with the minimum being 30 minutes. Others are $35 for 20 minutes. Some go up to close to $100. Some I feel I get my money's worth, some I do not. And, with my own financial situation, I was not always able to go to a "high end" reader due to the pricey readings. I work full time, but now do readings and reiki on the side out of my home. I advertise locally and through friends, as well as my day job. My prices reflect what I think is fair for what I offer, and also are not so high that people who feel they could benefit from my services are unable to afford me. I do not put a time limit on my readings, so I feel I can charge a little bit more since a timer doesn't go off and people are then left with more questions and no more time (that seems to be the "gimmick" in the region I live, not sure about everywhere else), but I choose not to leave people with more questions than they came with and also, I don't want to use a "luring" technique. The whole reason i am doing what I'm doing is to help people in my own way. I feel that with tarot readings, you almost take on the role of therapist or counselor in a sense, and I take that very seriously. Do I want to make some income from my services? Of course! But I also have been on the other end of the scene and I want to be able to provide something more for the people that come to me. So...in that respect, I feel that I offer a bit more than the typical reader in my area. Though I may not have the recognition that I'd like at this point in time, I know I'm moving forward with it because I get A LOT of word-of-mouth clients as well as repeat customers. I would say to go with what feels right to you. You know what you offer...what would you be willing (and also able) to pay for the services you provide. And what do you feel your time and energy are worth? Everyone is different...just because someone charges $20 doesn't mean they aren't very good, but a $100 reading may not be what someone feels is up to snuff either. So it's up to you to figure out your price range according to what you offer and know that it's going to work for some but not for all, and that it's what YOU feel comfortable with that will move you forward.
Good luck!!