i could be mistaken but i believe that i have often seen various transmutes going for free or really cheap in trade chat, which would make the profitability of it pretty low.  Im planning to make my alt an alchemist since he is almost level 70 and im having a tough time deciding.  Any raiding player is going to need a consistent supply of flasks or elixirs for advancing content.  At the same time, all players hardcore or casual need potions and they are a highly traded item on any server.  Since my other 70s are not alchemists and i have had to purchase fel lotus before, im wondering if converting easily found herbs to mass potions is profitable enough to overcome turning the rarer herbs into the minimum amount of elixirs, i.e. can i sell enough super manas/heals regularly to be able to afford possibly having a lack of flask mats at times.  Also, are transmutes more profitable than i have seen?

From what ive read all the specializations have a chance to create 1-4 extras of whatever it is you are making.  which means if you gather the mats for a skyfire theres a slight chance of ending up with a few of them.  naturally if you were to luck into 3 or 4 skyfires or earthstorms then you would have gained the equivalent of a dozen stacks of potions in terms of money at the AH.

right now im thinking that potions might be the best choice given that they have a constant high demand on auction and you will always need a few stacks of them, whereas diamonds are an occasional necessity and flasks/elixirs are raid oriented.