Over on the arborist site, a fellow who is supposedly a regular ebay vendor was alluding to a strategy of making a steep price change when an item is temporarily out of stock as a way to trick the ebay listing algorithms into holding your place in the listing priority list.
Basically, temporarily placing an extremely high price on an item insures that nobody will order an item you can't supply until your stock is replenished and still keeps you in the first few pages of a keyword search. When the vendor gets new stock, he simply returns the price to normal.
Seems like a b.s. way to game the system to me.