said by puppy:
I always went transmute because you can't chug potions in raids anymore, and flasks lasts very long time with the guild cauldron bonus (I assume it's still there).
Most medium - high pop servers can see flasks and potions be bought up quickly especially on Tues-Thurs nights which is when most guilds raid. If you're good, you're pre-potting. If you're progressing on a fight, you can go through stacks of pots after a few hours of attempts.
Guild cauldron bonus is gone. They removed it to discourage lazies in guilds from not worrying about bringing their own consumables (one of the few changes I approve of).
As for most profitable, probably flasks or potions. If the transmutes that don't have a time restriction sell well, then that's probably the way to go. I made most of my gold transmuting epics back in the end of Wrath.