"Hey Azuriel, where is the best place to farm Volatile Fire?"
It is one of the measurable milestones of any Auctioneer's life when they no longer have to worry about farming their own materials. When my friend was asking me the best farming spot for Volatile Fires, the AH was the first place I checked. At that time they were going for around 17.35g each at the cheapest, but there were probably 200+ Volatiles within a 17.35g-22g band. Is that a good price? Well, it depends on why you want some. If you were intending to put up some Scorched Leg Armors for 100g then, no, probably not. If instead you were hoping to replace an Etched-Fire Dagger that had just found a new 999g home, then yeah, those prices are not bad. My friend wanted to farm however, and so I sent him on his way to go fish up some Volatile Fire over in Hyjal.
Sometimes you are just in the mood to farm and that is 100%, perfectly fine. My recommendation though is farming via the transitive property. My friend wanted Volatile Fire and was willing to spend X minutes farming it. Since the AH has plenty at a subjectively reasonable price, if you really want to farm something, then farm something worth more - or easier to acquire - than Volatile Fire, sell it, and buy the Volatile Fire. Or more likely, buy the Fire now and sell what you farm later. "I'm not paying 18g for an item fished out of pools in Hyjal." Okay, cool... then why did you buy my Defender's Demoneye for 250g that I bought uncut off the AH for 45g? The Volatile Fire did not get any cheaper when you fished it out yourself - in fact, that personally-farmed Volatile Fire is probably more expensive considering you spent your otherwise valuable time doing it.
Farming via the transitive property is a fancy term for something most everyone knows instinctively on smaller scales. If you need Wool Cloth, for example, do you head down to Stockades and farm some? How about Copper Bars/Ores? Unless someone is being cheeky and listing Wool Cloth at 300g/stack, chances are you simply buy what you need with gold you got doing something else. There simply appears to be an invisible line after which a person's indignation (Khorium Ore at 60g a piece!) overrides their rational mind (Pyrite Ore is going for 60g per node) and they end up farming something out of spite... that doesn't affect the source of their ire at all, while harming themselves. Don't be that guy.