As I've been working with artists to build their websites, this question often comes up. Should I add prices to my art? I've done some research and did a small survey to see what others say about this topic. Some of the results are below. Hope this helps you.
If your art is in a gallery you may have to check with the gallery to see if it's possible to list prices on your website. The results of my survey concluded that if you aren't represented by a gallery then it's a good idea to add prices on all the art that is for sale on your website. If you are in a gallery you might be able to work out a good solution with them, especially if you have work on your website that isn't in a gallery. According to several sources I researched, not pricing your art on your website, but rather asking people to email or otherwise contact you for prices, is always a big mistake. Not all buyers and collectors feel comfortable asking and you don't want to miss out on sale to them. An option is to have a purchase or buy page, that makes it easy for people to know what's available for them to purchase, the price and how to initiate that purchase.
Some of the articles I read about pricing art indicated that it is best not to mix art that's already sold with art that's for sale. Potential buyers might get the impression that the best pieces are already sold and all that's left are ones that weren't liked. They may get frustrated when their favorite piece is already sold. A solution might be to show sold works under a separate category in the gallery or portfolio. This category might have commissions, sold work, art in private collections, public art, institutional collections etc... Showing past works in this way acts as sort of a pictorial resume and speaks to your experience, success and credibility as an artist. The results of my survey showed that all respondents felt it was best to have prices listed. Here are some of the responses they had about why buyers might not want to contact the artist for the prices: buyers may think that doing so will obligate them in some way, that the artist will give them a hard sell, that they'll get a barrage of emails, that they'll be embarrassed if they find out the art costs much more than they can afford, that artists will quote as high a price as possible just to see how much they can sell it for, and so on.
If you decide to have prices on your art be sure to clearly state what your return and refund policies are. The more willing you are to work with buyers, the more satisfied they will be. The absolute best way for you to get the word out about your art is through your website. Make sure yours is working on your behalf.