It can be lucrative, but situational, from my experience. I've cut gems for several people that had just completed the Shadowmourne quest line. And the other night, someone wanted me to cut 9 ametrines (which he didn't have). Sadly, I have absolutely no stock of epic or rare Northrend gems, so I couldn't cut or create what he wanted. So there is a market, but I think you probably can only take advantage of it if you happen to regularly be in the trade channel where you can happen to catch someone that's looking for those gems.

Not particularly valuable. They can be useful if you also have jewelcrafting, but they're not very helpful for leveling and rather obsolete at max level, so there isn't much market for them.

Yeah, so transmuting Cardinal Rubies instead of Volatiles...no.

My main has been an alchemist - swapped from Potions to Xmutes in WotLK.
Took 2 of my alts, dropped from one herbing and skinning from the other and powerleveled Alchemy on both over one weekend about 6 weeks ago for approx. 3K gold, went Potion Mastery on both, dropped it and paid the gold to go Xmute so I can get the 45 volatile xmutes per day. Profit approx. 180- 200 per day each toon.

You find a 150-200g price differential between that quantity Volatile Life vs Volatile Something Else?

Of course, 150-200g < one full set of Firelands (or other cataclysm) dailies. In the long run, not a great loss.

@erik

Yes, at times the cost difference between life and air can be 20 G per volatile