[Siren's Tear] One item that can net you 300g each.(Kind of depends on realm's the fuller the better).So why is it such a gold maker...
Well coz its used for:
Tailoring: [Deathchill Cloak] - Caster DPS Cloak
Requires [Loremaster of Northrend] to train
Tailoring: [Wispcloak] - Healing Cloak
Requires [Northrend Dungeonmaster] to train
Jewelcrafting: [Enchaned Tear] - Unique Equipped +6 to all stats gem.
As you know the cloak's are one of the best items...sometime they last deep in Ulduar. Also sell for 1000 and up ...
The only rare material for crafting these cloaks would be the [Siren's Tear]. They usually don't appear on the auction house very often and when they do they are tend to be expensive. Sometimes hey go up for 800g on my server.There is a high demand for these cloaks as well as for the [Siren's Tear]. As for now only couple of tailor's can make this items. This involves doing the majority of the quests in each of the Northrend zones and/or clearing all the new Northrend dungeons and this takes long time so dont expect many people to have this. All the reasons I listed above only add to the rarity of the cloaks being made, so the price will stay the same for very long time. Even if people find all the easy materials for one to be crafted, [Siren's Tear] will usually stop them in their tracks. If you want to have these crafted for resale, the materials will cost roughly 500g not including the tear your going to profit about 500g. It is a pretty sweet deal, that is if you find the tear for cheap or farm one yourself.
How to obtain one
Over in Borean Tundra, there is a vendor named Ahlurglgr <Clam Vendor>, that sells these. However the currency used to buy them is not gold, but 100 [Winterfin Clam]'s. These drop off various Murlocs across the water as well as spawning on the ground and in the water. At level 77, I was able to farm 80 clams in under an hour. I have the add that the tear is limited I don't farm much, but killing Murlocs and collecting these clams wasn't so bad. The tear itself is worth a lot in some cases and is used to craft epic cloaks which sell for even more. While farming, the mobs also drop money, greens, and your regular clams all nice for some more cash . The nice thing the new clams, [Brooding Darkwater Clam], is that they have a 33% chance to drop a [Siren's Tear], as well as [Northsea Pearl] and [Succulent Clam Meat]. The chance of the clam to drop is less than 1% however and this makes it very very hard to farm. There is also another type of "open me" clams that have a higher drop rate and contain the pearl/clam meat. If you like fishing i recommend staying in Wg and fish some fish also you get the clam.In WG drops all the fish needed for [Fish Feast] (the best mass raid buff food) So you can sell the fish for nice profit too. But back to Borean Tundra farming murlocs dose give Winterfin clam but they also drop decent vendor trash, green items, fast re-spawn times, and easy to kill mobs, you get a profitable farming area. As a side note, if your a Rogue, you can also pickpocket these mobs for [Reinforced Junkbox], which in a very rare chance, it will contain an epic weapon or a rare gem.
Profit
Once you get one, assuming your going to craft a cloak for resale, you have spent about an hour farming/buying mats and will profit an estimated 500g. So essentially, your averaging 500g an hour doing this. If your able to sell a [Siren's Tear] for over 500g, you can skip the whole buying mats and crafting part. The 5 [Bolt of Imbued Frostweave]that are required for these cloaks may be expensive. I recommend finding someone to disenchant your greens and process the cloth for you. I have sold about 10 crafted epics so far for a profit of 5000g, part of my success is diversification. I chose about 5 different BOE epics to craft. I also do not make more than one of each item at a time, this is just in case the one doesn't sell and that the price of the mats may do down. These BOE items only sell so fast, there is a very good chance you may have to re-list the item, sometimes with a lower price to undercut the competition. What's that, you dont have a crafting profession or are not high enough yet? No worries, most people are eager to level their professions so you can just have someone else do it. They may even pay you if they gain a level! As for tipping, most don't charge very much anyways. Good luck with crafting your BOE epics and we hope it brings it plenty of gold for that [Reins of the Traveler's Tundra Mammoth] you have been saving for.