SET A PRICE AND STICK TO IT!
Once you have set your price, stick to it! If you think that your artwork is worth a certain price, don't let anybody talk you out of it. Lowering your prices for some but not others can not only devalue your work, but can also give off the wrong impression to customers about your professionalism. If you notice that more people are questioning your prices than are buying your artwork, it's probably time to reconsider how much you're charging.
RAISE YOUR PRICES AT THE RIGHT TIME
Once your artwork starts to sell, it is natural to start to reconsider your pricing. At this point, it is a mistake to raise your prices dramatically. This can be particularly damaging to relationships that you have built up with loyal customers over time. If, after 6 months of selling regularly, you decide to raise your prices, it is important to do this gradually.