I have found it depends totally on your area. For an unsigned (no gallery) artist, you want to price things comparably to what you would see for similarly sized and genre pieces in other stores or people's shows, depending on venue-art fair, local gallery, and so on. You don't want to be the only cheap amateur, but you don't want to be way out of everyone's league if it's inappropriate. If you feel a "fair price" is not worth parting with a piece-don't sell! Therein lies the conundrum. If you really want to sell, then I would be sure to charge 3X cost or a fair sum for your hours above materials (but this often bumps things "out of people's league" unfortunately). So use your judgment based on what type of people you are selling to, the venue, the competition, etc.
I don't sell anything locally because in our area no one would pay even $100 for a painting, and mine take months to do and I use gallery quality custom linen canvases which are sometimes a few hundred $s in themselves not including paint and hours spent. So I take commissions from out of state. Work I see selling well here is very inexpensive if you can swing it and if it's fair to yourself.