Hello, Here is how I would go about pricing artwork. First ask yourself how much your time is worth. How much do you want to earn? Once you've answered these questions, you should worry no more.
You do not need a degree in art to create art. As long as you have the desire to achieve your goals and the skills in order to meet them, then you are all set! Good luck with your next project!
Muralist~ D. Windseth