I was in high school when I first read Extinction: The Causes and Consequences of the Disappearance of Species by Paul and Anne Ehrlich. It was an epiphanous experience. One of the most stirring images described by the Ehrlichs was that of the Keystone Species.
Within any ecosystem there are species that are so integral that their extinction would cause the entire ecosystem to crash. Removing Ochre Stars from the coastal California marine ecosystem would lead to an explosion of mussels, whose proliferation would crowd out all the fish, sea lions and eventually the coral beds. The Ochre Star is a Keystone Species for that ecosystem.
Within WoW there are certain Enchanting materials that similarly hold the key to ensuring the stability of their relative ecosystems. My purpose here is to identify three such materials and to give strategies for controlling those materials to maximize your gold earning opportunities.
Large Brilliant Shard
Large Brilliant Shards are a 100% drop from certain blue items, level 56 to 65. Some blues below that level will give Small Brilliant Shard but unlike other Shards and Essences you cannot combine 3 Small to get one Large. Further increasing the rarity of the Large Brilliant Shard is the very small farming area: Blackrock Spire (Upper City).
Back in the day (it was a Wednesday) you could farm these from Dire Maul and Strat. Not any more. Post-Shattering the only place to farm them is UBS.
You can craft certain greens that will give a 5% chance of dropping a Large Brilliant Shard but this is a roll of the dice. It also may not be cost effective. Look at Tailoring, Leatherworking and Blacksmithing patterns in the 52-59 range. You will find things like Thorium Leggings (BS), Wicked Leather Headband (LW), and Runecloth Boots (Tailor). As far as I could tell these three items have the lowest material requirements of any green items including the JC rings and necklaces. On other servers prices might make other greens more cost effective. Research yours.
Thorium Leggings (17g), Wicked Leather Headband (28g) and Runecloth Boots (11g) all have the same 5% chance to drop a shard when DE'd. The other materials that are more likely to drop are Greater Eternal Essence and Illusion Dust. Depending on your server, these may be profitable enough to consider mass-crafting and DE for the chance of grabbing a Large Brilliant Shard.
To test this, I crafted 96 Runecloth Boots today and DE'd them all. I selected the Boots because I had hundreds of Runecloth Bolts and a ton of Rugged Leather stacks on hand. I got back 29 Greater Eternal Essence, 61 Illusion Dust and 4 Large Brilliant Shard. The Greater Eternals trade for 20g each (580g) and Illusion Dust go for 5g each (305g). If I had bought the mats I would have spent roughly 1,050g so this would have been break even at best.
Large Brilliant Shards are used in some of the highest retail price Enchants being sold now. It takes 8 of them for Enchant 2H Weapon - Agility which sells for 750g. It takes 6 of them for Enchant Weapon - Mighty Intellect which is going for about 450g. It takes 4 to make Enchant Weapon - Healing Power which is selling for 350g.
Undermine Journal lists selling price for Large Brilliant Shards at 39g each. I have seen them sell for upwards of 50g. They never last more than a few minutes when they are listed because the few Enchanters who are active in these key scrolls have alerts set up. Whoever gets there first usually buys them all.
I usually don't endorse farming, but a run of UBS takes my Pally about 45 minutes and yields 10-12 shards. Add to that all the greens and cloth that drops and this run is easily worth the time. Remember, I never re-sell them and use them instead to craft scrolls. Farming UBS for an hour gives me an estimated 1,500gph, which is worth my time.
If you plan to become active in this market, set your alerts in TUJ and buy any that appear below your threshold. As a re-seller leak them out as singles for 125% to 150% of market value only listing 3-4 at a time. Don't worry about undercutters. These will sell as long as the buy price makes it only marginally more attractive to pay you than to go farm UBS.
As a crafter, you need to see which scrolls are selling best and only use your supply to craft for the best return. This may not be the highest list price.
Pre-Shattering, Abyss Crystals were selling for 4g to 8g each. I missed the mark on Glyphmas. I didn't buy a lot of the predicted "sure things" as WoLK ran down. But I did stockpile as many Abyss Crystals as I could buy when folks emptied their banks. I had at one time a full bank tab and about half of another one just of Abyss Crystals, around 2,500 or so.
They were gone by the end of January.
I sold some, Shattered others for the Infinite Dust and Greater Cosmic Essences and used the majority on the scrolls that have sold so well.
Berserking, Accuracy, Blade Ward, Greater Spellpower, and Powerful Stats have all been very good sellers post-Shattering. Although these do not sell every day and the market is fairly unstable in terms of price consistency, I can count on selling 3-4 of each of these every week. For example, I have sold Berserking for as low as 450g a few days ago to 735g yesterday. Greater Spellpower went for 399g today and for 575g last week. Powerful Stats sold Saturday for 143g but sold for 105g a few days before that.
I attribute some of the popularity of these Enchantments to the wildly overpriced Maelstrom Crystals. For the best Enchants in Cataclysm it takes 3-5 Maelstroms. At 1,800g each it is just not cost effective to pay 10k gold or more for an enchantment that will become obsolete in a few more dungeon runs. Thus, many players are using the WoLK chants--less flashy, but still better than nothing.
Abyss Crystals are farmable in WoLK dungeons. They DE 100% from Epics and now from PvP gear as well. Abyss Crystals are not cost effective to "craft farm" by crafting an Epic just to DE it. However, as guilds are running more and more WoLK instances to earn achievements and even for nostalgia there has been a fairly stable supply in the AH.
The cycle I'm seeing is better availability Thursday/Friday with prices running about 15g each and then very low, spotty supply on the weekends and into Monday with prices running 25g to 30g each.
You may not be able to control this market due to the sheer volume of Crystals that come into play. Unless you are willing to spend 25k to 40k gold to buy up all the supply for a week or more and then slowly leak back the inventory my suggestion is to ride the waves. Go on a shopping spree late week and buy all you can for 15g-20g.
Use your TUJ alerts for your buying and selling indicators. Set all your auctions at 12 hours and don't worry about undercutters. For best sales results, list 75% of your auctions in stacks of 4 and 25% in stacks of 2. Almost all the recipes call for even numbers of Crystals--buyers will buy a 4 stack and a 2 stack or two 4 stacks at higher prices than they will buy 8 units at lower prices. I don't fully know why, but that has been my experience.
As a crafter, the lower your acquisition price the more flexibility you have for setting your retail price. There are lots of different philosophies on whether deep undercutting or setting a ceiling is the best way to go--and I'm not going to worry about that here. If you buy low you can craft and either sell low for quick gold or sell high and have more profit.
If you are a re-seller instead of a crafter be on the lookout for fluctuations in the sister markets of Infinite Dust and Greater Cosmic Essence. An Enchanter who uses Abyssal Shatter will 'break' an Abyss Crystal into either of these two sister materials. There is a ton of debate about how many of each result from the Abyssal Shatter. I have seen from 5-15 Infinite Dust or 3-7 GCEs. ((you get either material per Shatter, not some of each)).
As a re-seller, consider Shattering some and reselling the Dust and GCE. At 5g per Infinite Dust or 18g per GCE (average prices on my server) a 17g Abyss Crystal could yeild 50g worth of Infinite Dust or 70g worth of GCE. Experiment and see what your results are--but usually, if you are buying Abyss Crystals for less than 40g each you will see good profits from Shattering them. Sometimes these profits will eclipse your flipping profit.
Essence of Air
Ah, the bane of my existence. No other crafting material causes me more frustration than Essence of Air.
Much like Large Brilliant Shards this material is used in specific, rare Enchantments. Unlike the other materials we have discussed there is no way to get Essence of Air other than to farm it or buy it on the AH. There is nothing you can DE to get it.
The recipes it is used for are fairly rare. In fact, there are only 12 patterns that call for Essence of Air. The Stormshroud Armor set uses from 2-4 Essences for each piece. As a high end L55-59 Leather set, this armor gives +Agi and +Crit for Rogues. Each piece in the set sells for 125g to 200g.
There are some other armor and a couple weapons that call for Essence of Air. However, the big ticket items are the +Agi Enchants. One of them we covered above, Enchant 2H Weapon - Agility (selling for about 750g). The one-handed version, Enchant Weapon - Agility is a +15 Agility chant that is also going for 750g or more. Each of these enchants takes 4 Essence of Air to craft. The final Enchant, Icy Chill, only takes one Essence and sells for under 100g.
Also note that the one hand Agility chant is usable on heirloom weapons.
The only place to farm these Essences is in Silithus, in the northwest section where you find the wind elementals. The drop rate used to be about 15% but post-Shattering the drop rate is much lower. My estimate is around 3%. You can do your own research about what the drop rate actually is. I have farmed here for over an hour and gotten 2 Essences for my time.
I seldom see these in the AH but when they are there most of the listings are 125g and up. That is each, I might add. Occasionally someone will list for way under value because they don't know any better and I grab as many as I can when that happens. I can buy them for 50g each and make money on my Agility scrolls. For 125g it isn't worth the effort.
Once upon a time, you could learn the spell Transmute Water to Air from the ghost quest giver in Scholomance. That would let an Alchemist transmute the much more readily available Essence of Water into an Essence of Air. However, Blizz has removed that questline post-Shattering and has no interest in reviving it. Of course, I never got that transmute on my Alchemist--one of only two or three he doesn't have.
My advice on Essence of Air is to buy them when you can but unless you have nothing better to do or are just really, really bored do not bother farming them. If you do, list them for whatever you can get. The sky is the limit.
Keystone Materials Finale
I hope this helps you in some way. There are other choke points (or Keystone Mats) in other professions. In my opinion, there is none so dependent on very specific, hard to gather materials as Enchanting.
Good luck, and happy hunting!