Christopher, I like Christines approach. first ask why? what do you gain or want from a sliding scale that you feel you are not getting from a flat rate?
I also like Karin’s response. Offering half hour and or small group training provides them a price point they can afford without sacrificing what your time is worth.
I wise man told me once “You can only give so much to charity before you become the charity”
Honor yourself and pricepoint fairly so others do not take advantage. Then you can afford to work with people who really need your time and deserve your charity.
Hope this helps…