Being an artist is a business, understand that. And in business pricing is, after all, an art more than a science; ask any businesspeople especially the ones involved in a startup.
There's a business principle about selling anything that states that the price will be "whatever the market will bear"; so, price your art whichever way you want, if it sells a lot, increase the price, if it doesn't sell much, decrease it. If it's not selling at all, there's not a market for your art, could be timing, could be the wrong market, could be something else.
A few additional readings for you:
this book has good guidelines and some examples.