Posting prices on your website is a deterrent for art dealers to play hanky panky — charging their clients higher prices than the ones you agreed upon. Beware of art dealers who have a hissy fit about having your prices posted online.
Although some artists worry that posting prices makes a site look too “commercial” — this train of thought is a leftover attitude from the 1990s. Yawn!
I do not recommend posting prices directly next to artwork. I want people to concentrate on your work — not the price. But a price list on a separate web page is very helpful. It also acts as a filter — eliminating people who are really in the poster market and have an unrealistic sense of how much artwork costs. And it will save you precious time, not having to contend with art dealers who have a glass ceiling regarding prices– and only sell artwork for very meager amounts and expect you to conform.