One of my favorite enchanting markets involves heirloom enchants. While they may take certain miscellaneous items like Essence of Air or Righteous Orbs they pretty much all take a few common components: Greater Eternal Essence, Illusion Dust, and Large Brilliant Shards.
No, I'm not going to rehash the same tired Enchanted Thorium Blades and Runecloth Headbands post, though you can certainly integrate them into this little shuffle I'm about to introduce. You see, I hate Enchanted Thorium Blades. Rugged Leather and Thorium Ore are rarely in abundant, cheap supply on my server with so many people leveling. Doing only Runecloth Headbands will give you far more Dust than Essence. What's an enchanter to do?
It's time to visit Gorn One Eye. Never heard of him? That's because he's being sneaky and hiding behind this tree root in Timbermaw Tunnel:
Now, any enchanter into heirloom enchants is already exalted with Timbermaw for the Agility enchants. If you're not go get it done, since Cataclysm it's crazy nerfed and won't take you long at all. Gorn will sell you an item called the Furbolg Medicine Totem, a one handed mace which will cost you about 9g 31s with all discounts applied.
I bought 50 of them (465g78s50c spent) and DE'd all of them. They DE into Lesser Eternals, Dream Dust, and Small Brilliant Shards. This is what I ended up with.
There are very few uses for Small Briliants so I turn those into +100 Health to chest. They move slower and for less than +4 Stats but since you can give them a lower price tag they can be attractive to the thrifty alt.
On my server right now a Greater Eternal is 41g, so leaving aside the shards and dust I can already sell these items at a 400g profit and all I did was visit a vendor. I didn't need to rely on anything on the AH and could essentially do this endlessly.
However, I do this for enchanting materials. Now, Dream Dust is virtually useless as an enchant material but can be "traded up" in a few different ways. The most popular way to do this is probably Enchanted Thorium Blades. That tends to net more Eternals (not a bad thing.) So be sure to have Rugged Leather and Thorium Ore and Bars on a snatch list. Also consider Wizardweave Robes, though they are not very efficient, they're just a way to get rid of way too much Dream Dust without flat out destroying it should you be unable to find enough Thorium/Leather.
In short, this is a way to always get unlimited Eternal Essences without having to worry about depleting your AH of the materials necessary for the blades and headbands and the like. Unlimited essences are at your finger tips!