Hello. I have just recently started playing wow again and started herbalizing again and i checked the auction house for how much some of the old herbs i used to sell cost and was really suprised. what caused the herb prices to go down so much?
Low demand. Newer expansions bring new recipes which require new herbs. There's little need for older herbs except for leveling a profession or if you're going to play around that level range for a while, like stopping your xp gain for a pvp twink. At the same time though, some old herbs can be more expensive on the AH than newer ones because of low supply. There's a lot that goes into it, but mostly it's because no one wants the old herbs as they're obsolete and not really used for anything meaningful at end-game.