We have been selling on ebay for several years and were about to cancel our store because it wasn't working right when we figured out the formula. This works VERY well for antique and collectible sellers. When we go to auctions and there are several things that are similar in era, style, color, etc., we buy it all. We then make an exclusive store category for them. Then, we take two or three of the higher priced items and send them to live auctions. The other ten or fifteen items we put in the store. That way, it keeps the fees lower and all of them cross promote one another and our store soon becomes empty. Another tip is to price your items about 5-10% lower in the store than all of the closed auctions you researched for the identical items. They will ALWAYS sell if you do that. An example: we purchased about 30 vintage Jim Beam whiskey decanters several months ago, put the most expensive in live auctions, put the rest in the store at prices that were just below the average ending price for identical decanters the week before, put a best offer also on them, and sold them all within two weeks.
Another tip: If you are selling a swedish modern sewing box, put it in a category with other things that people who like Swedish modern would be interested in, not necessarily other sewing items, but other "modern" items. It works every time because it gets them into your store, and once there, they buy something else a lot of the time.
Another tip: if you have ten pieces of Imperial glass, or thirty pieces of depression kitchenware, list it all at once. Don't list 2 or 3, wait until they expire, and list more. More collectors will shop in your store if you have a lot of what they collect.
Good Luck and thanks for reading.