Offering different things with a range of prices works pretty well for me. Doodles starting at 99 cents, Simple Drawings/Paintings at $5-$15, more complicated stuff higher...
I'm no expert, but I would say when first starting selling ACEOs, think of the first few batches of sales as building your reputation and feedback. Offer them starting at a competitive price (say $5, maybe $10 or even higher if it is really really awesome and you just KNOW no one could pass it up) Don't espect really high prices immediately. If they all sell without any relisting (even with just one bid), or all get many bids, you may want to increase your starting price by a few dollars. If the next batch sells without any problems, increase a little more, and so on until you reach the minimum price you really really want. If they don't all sell, relist once or twice at the same price and if they still haven't sold set them aside (maybe for a month or so) and make and list some new works. Then after a little while, list your unsold works and buyers who might not have been around the first time you listed will see them and might buy them.
If you list something and it doesn't sell, don't lower the price or the eBay buyers (who often tend to be looking for a "bargain") may just decide to wait on EVERYTHING you have until you lower the price.
One exception to not lowering prices is to occasionally offer (maybe once a month, or even once a week if you do a lot of work and regularly have many new offerings) a great deal. If you are doing something as a promotional "sale" with a lower than normal price, say so in the listing title (*sale!!* or *low $$* or something) and it gets attention from buyers who might not have even noticed your work before (also, if it ends for a low price, as long as the detailed info and price show up in your feedback it's still marked "sale" or "low $$" so buyers checking feedback know that is a low price on purpose). I occasionally start my paper sculptures at 99 cents and have one day or 3 day auctions (or a week sometimes too...). These have led to many future sales - after the buyer receives their ACEO they see that is really IS worth a lot more and they come back and buy more at my regular prices. I might take a "loss" on one card and generate 5 more sales (4 winners of my "sale" auctions have even become fairly regular buyers of my more expensive items). There is a difference between a "loss" and cost of promotion...
Hopefully that made sense... Basically all of the above is what I did/do, and I think it worked/works great for me...
Matthew
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Edited by papermatthew at 09/26/2008 4:08 PM PDT