Buying Items at a Discount
You've heard me talk in the past about buying things wholesale like illusion dust, saronite bars, infinite dust, etc. and then turning around to sell them one at a time without flooding too much. Well there's an interesting item which you can get away with selling in bulk for more than individually.
Let's take a look at the lovely and shiny Abyss Crystal. This item is needed in stacks of 10 for several major weapon enchants, thus players will opt out of buying 10 individual crystals for the ease of clicking twice to pick up one stack of 10. The buyer is usually someone running to the ah to get the mats needed for an enchanter they're going to tip for 50 gold to make their enchant for that new weapon they picked up in ICC. Why not provide a small service to these players by posting 10 abyss crystals at 125% value? I'm sure they'll appreciate the less clicking and you'll appreciate the increased sales.
Give it a try, the deposit is 0 after all and the worst case scenario is that you sell back the abyss crystals for a slight mark up one at a time to cover the cost of the experiment.
If you find yourself with tons of abyss crystals and are unable to sell them, perhaps you should look into shattering them for dusts and essences. I will look to do this particularly when cataclysm arrives and people are looking for dusts/essences to level with.