Later you had crystallized fire that combined into eternal fire and back, while their prices never aligned and you could make bank on one of them by buying the other and combining.
My final memory of this nonsense was from before I stopped playing: in Draenor, you had a daily quests where you had to deliver 10 baubles that you got from filleting raw fish. All you had to do is buy lots of fish, fillet them until you got your 10 baubles, list them on the AH instead of delivering to the quest NPC and fillet again. Since filleting fish was slightly profitable on its own, everything the baubles sold for was pure profit and they sold for bizarre prices. Well, until Blizzard closed this by making the baubles soulbound.
I assumed they finally learned their lesson that morons and slackers are unable to plan or research and run to the AH where goblinish individuals make stupid amount of profit at their expense. While being that individual was fun, it’s clear that people making extreme profit at the expense of other players in a game that isn’t marketed as ruthless PvP is bad. Add that WoW tokens are now a thing, market isn’t a for-itself minigame, but something that affects real money.
My assumption was that they won’t do ice cold milk again, but seems I was wrong. The turn-in quests demand one specific item, without even chance to prepare in advance. So the only way to prepare is what Azuriel does: prepare for everything by having a huge stockpile of materials. That’s great for those who love market PvP, but everyone else is left behind, even if he is not a moron or slacker. When the quest appears out of the blue, you can’t do anything but pay whatever price the AH has (if you farm the item, it still costs the same, in opportunity cost).
The solution would be obviously to offer several options for turn-in. They should accept several kinds of items, so players can always donate what they can easily obtain. Or to announce what will be needed later. Or most simply: ask for a little bit of everything from the raw materials.
Let’s add this to the long list of “Blizzard didn’t really think this trough”.