I make the Sinister Combatant's Intuitive Staff (https://www.wowhead.com/spell=282343/sinister-combatants-intuitive-staff) for 20,000g and the materials are 13,000g or less. This makes a single expulsom worth 7,000g, plus or minus a few hundred due to the staff's deposit, AH cut, returns, and variance in materials. It still remains well above 5,000g and I think some people buy and resell my staves because the secondary stats matter.
Level 120 comes and goes. Island Expeditions have unlocked, but it turns out they’re not much fun, and the most rewarding versions are only accessible to premade groups. You turn to Warfronts only to realize they’re not available this week. Fine. You can always grind out better gear. Except as you do, you notice your new gear has higher Azerite requirements than your old gear, which means your shiny new items have fewer unlocked traits than what they replaced. Discouraged, you decide to roll as one of the cool new Allied Races. Except you can’t because they’re all locked behind reputation grinds.
Baelgun-Alliance-USBaelgun-Horde-USBalnazzar-Alliance-USBalnazzar-Horde-USBarthilas-Alliance-USBarthilas-Horde-USBlack Dragonflight-Alliance-USBlack Dragonflight-Horde-USBlackhand-Alliance-USBlackhand-Horde-USBlackrock-Alliance-USBlackrock-Horde-USBlackwater Raiders-Alliance-USBlackwater Raiders-Horde-USBlackwing Lair-Alliance-USBlackwing Lair-Horde-USBlade's Edge-Alliance-USBlade's Edge-Horde-USBladefist-Alliance-USBladefist-Horde-USBleeding Hollow-Alliance-USBleeding Hollow-Horde-USBlood Furnace-Alliance-USBlood Furnace-Horde-USBloodhoof-Alliance-USBloodhoof-Horde-USBloodscalp-Alliance-USBloodscalp-Horde-USBonechewer-Alliance-USBonechewer-Horde-USBorean Tundra-Alliance-USBorean Tundra-Horde-USBoulderfist-Alliance-USBoulderfist-Horde-USBronzebeard-Alliance-USBronzebeard-Horde-USBurning Blade-Alliance-USBurning Blade-Horde-USBurning Legion-Alliance-USBurning Legion-Horde-US
The last farm on this list, actually I was surprised this farm eluded me for so long. Generally speaking gnomergan is a huge confusing instance that takes some getting used to but if your a high value transmog farmer this does not scare you. You can pull the entire instance and get access to a plethora of high value loot such a recipes, world drops, greens and even engineer supplies. Overall this farm is shadowed by the Diremaul farm and Zulfarrak farm, but is an equal change of scenery with a wild card if you get the hot shot pilots gloves OR the mechbuilders overalls worth 400,000g and 60,000g respectively. A pretty cool neat farm that noone really mentioned until now.
From “The Burning Crusade” expansion, weapons like Klinge der Zauberei, Die Nachtklinge and recipes for different weapons are really valuable. The best example is Pläne: Teufelsstahlangschwert, worth 500.000+ Gold. These items are World Drops, you can find them in all raids and dungeons. I don’t know any Open World Drops, but that does not mean there are none. Another great transmog source are world bosses and rare spawns on Outland.