1) Unlike items, you can cancel your auctions for consumables at any time. This means that you can always free up one of your valuable auction slots at a moment's notice. Did you price that flawless topaz too high? No problem. Cancel it, stash it, and relist it. A bad item auction however will clog up your auctions for two days.
2) People are getting scammed by the UI. I figured this out immediately, but I can see where the confusion is. Here's the 'scam' that Blizzard is running:
- Search for an item with a quantity of 1, such as 1 chipped ruby.
- The price for a single gem will appear along with the average.
- Click buy. If the price has gone down since your initial search you'll get a refund. If it has gone up (someone beat you to it) then the buyout will fail. Chances are you'll get the chipped ruby.
- Click buy again. You've just consented to purchasing a second chipped ruby at any price. It makes sense, and I never fell for it. But lots of people are getting suckered.
So make sure you always refresh your search after each purchase. Never undercut on gems because some poor guy will misuse the UI to overpay every single time.
3) Use other people's low prices to advertise your higher priced gem. Either the 'scam' will sucker someone into paying more for your gem, or they'll buy in bulk. Say for example someone orders 2 chipped rubies, this time on purpose. Blizzard will say "Okay sir, your total is 1400g." That's a good price, so the buyer finalizes the transaction. But the buyer doesn't know or care that the 2 rubies came from two sellers who charged 400g and 1000g. If the buyer had seen a price of 2000g, then maybe he wouldn't have bought those rubies? Your anonymous partner just did you a big favor.
Also, like crafting materials, gems are drastically under valued right now. It's probably because no one has any gold! In one quest in late normal I might earn 10-20k between the reward and drops. Apparently a radiant gem is worth 15 minutes of work in normal difficulty? Even though radiant gems drop less frequently than one every 15 minutes in late NM? I think that's wrong. Radiant gems are very powerful for their current price. And there's no level requirement!