I have struggled with the feeling that charging for what I do is wrong... it's a very deeply ingrained belief, in pretty much everyone! I'm at the stage of getting it with my head, not yet my heart - but two ideas have been helping me and I'm coming closer to feeling that's it's ok:
1. If we keep ourselves poor or with just enough to get by, we have nothing to give or to share. If I want to found that charitable trust or international prize or school, I need to have the wealth to do it.
2. When people pay, in fact the more people pay, the more likely they are to put something into practice. If you want to help people for real, remember that they may have an epiphany or be deeply moved by your reading, but if they've paid they are far more likely to act on what they learnt.
As I say, these are still things that I have to keep telling myself - they are true, yet my block about charging (not only for tarot but for other things) is a very solid one. I am working on it! But I now understand that working (giving hours, giving any kind of value) for free isn't a virtue. I do think it's important to be able to waive the fee when someone can't afford it and so on, or have a sliding scale or something like that. Maybe leave the amount up to the querent - I like that idea. A lot of authors sell ebooks now with a "pay what you think it's worth" PayPal button and that depends on people coming back after they've read the book - and this *still* makes money. Believe it or not, people like to pay when they receive.