I'd say alchemy or maybe inscription. (My priest has 270 inscription no herbalism and I only spent around 50g because glyphs sell back)
Leatherworking (since it's ridiculously easy and cheap to level at higher skill levels), inscription or alchemy will usually be the cheapest on any given server simply due to the low mat requirements.
Unless you have an economy that's extremely favorable to buyers, JC will be pretty expensive unless you can DE everything you make and sell it back on the AH. Even then you won't come out ahead at all. I assume you will be flasked in a raid environment, in which case alchemy will be equally beneficial as JC anyway, not to mention it will save you money with double duration flasks.
Alch IMO with all the different pots and flaks you can use will save you alot of money in the end and earn you alot. Also if you need help lvling it asin guide. Here i used this for my alch, ins, ench, and engineering.. Very Very accurate.
http://www.tarouwowguides.com/