No idea about leatherworking - AQ borked leather prices so it would be expensive now (200+). Refined deeprock salts go for 15g on my server.

Tailoring is prolly ~100g to get to 250 for a 20g cd on my server
Alchemy is sameish but arcanite CDs are worth like 5g... and you have to go through the trouble of 'selling' them. The heart of fire > elemental fire xmute is nice, but you have to grind incendesaur scales, too.

As of right now, I would say tailoring is the only surefire way to make your gold back quick. I would say level alchemy if you expect to be heavily invested into TBC coming out. Having multiple tailors / xmute alchemists in BC will be VERY valuable for the first month of TBC.