There was a thread in here a little while ago about RL life pricing and how much people would be willing to pay real money for good custom art. Most said between $15-$25. I set mine between $50 - $100. But my bias is that the only time I would pay for art made by someone else would be because the artist is operating with a great amount of skill and is taking their time, skill, and effort, not to make something for themselves, but to make something for
me. And this is a type of service I can't just go onto amazon.com and buy like your typical commodity.
Actually I find that what you really are buying from the artist is time and effort, which is independent of skill level. Even if its the most novice of artists, if they really slaved away over a piece to the best of their abilities it becomes worth something. Whether someone orders the work or not is made by the buyer
before it is made. If the time and effort has been expended then it is the buyer's responsibility to compensate for that.
So the artist should set their price based on how much effort it is going to take to complete the type of art the artist is selling. If someone thinks its too high, then they're not worth your time because they obviously don't appreciate what you do.
At one point you were able to get customers and you say now your customer base has dwindled. Obviously at the start of your shop there were some individuals who thought your prices were fine. My question would be if anything has changed in the art you're producing, or if your shop is getting bumped enough to be visible by more users. Working on your shop layout is also a nice touch. Make your shop look nice, thought-out and professional, and keep your samples well stocked.