Approximate earnings: Upon successful acquisition, between 15 and 18k per unit.
How to: There are 18 individual items that are necessary components of a quest called Auctioning for Parts (Alliance) / Auctioning for Parts (Horde) which unlocks access to an auctioneer that can be used at the Trading Post building in both Horde and Alliance Garrisons.
The majority of these are easily obtainable, and therefore not very valuable. However, the items that are required to create the Universal Language Module are still highly desired and will sell for anywhere from 15-18k a piece. The only place to farm these is Ashran, a PvP zone located in Draenor. Characters level 92+ can visit their faction outposts (Stormshield [Alliance] / Warspear [Horde]) in Ashran but cannot participate in the battle.
The good news is that all the mobs and lootable players have a chance to drop the three components that make up the language module:
The drop rate is low, but it is still a worthwhile farm if you happen to enjoy large scale PvP at end game.
Tip: Portable vendors make a great addition to any farmer’s arsenal of efficiency items. A few options to consider: Traveler’s Tundra Mammoth, Grand Expedition Yak, Jeeves, Walter, Repair Bots 74A and 110G, Guild Page and Herald, and the Argent Squire.