Ok, so what we need:
1. Someone lvl 60+
2. Enchanting skill 225+
Ok, it is simple, go in Halaa that is in Nagrand and buy [Avenging Blades]=2 Gold 21 Silver 42 Copper and [Halaani Claymore]=9 Gold 24 Silver 63 Copper, from Aldraan
Blade Merchant and then desenchant them, in 90% of it from [Avenging Blades] you will have 1 Greater Planar Essense and from [Halaani Claymore] you will recieve 2 of them, and still you have like 2% to get Large Pristmatic Shard.
On my server Greater planar Essense on AH costs 10g per one.
And vendor sells 3 of each item, so this means that if you will desenchant 6 items and then sell mats on AH you will recieve 10g from each Greater Planar essence (and you will have like 5 of them for sure).
Respawn time for those items is not big, 5 min an most.
In short words:
1. go in Nagrand, Halaa
2. Buy [Avenging Blades] and [Halaani Claymore].
3. desenchant them and sell on AH.
Sorry for my bad english, and ye this is my first post =)
And sorry if this is common sence.