With Jewel crafting I make 1k gold a day. There is two veins that spawn by Dawstone village in Quel that I mine for about 1 hour or so. I get about 100-130 ore of Adamantite, a stack or two of Khorium, 2-3 stacks of Eterenium (sp), about 10 primal earths, 1 primal fire, 2 primal mana (from killing the sentries between the two spots, tons of cloth off the undead guys, varied greens and vendor junk.

The veins spawn 2-3 min apart from each other once mined (There is also another spot on the way to the bombing run that spawns every 3 1/2, usually Rich Adamantite vein. But on my server its useless because it is camped by a guy that works from home, so he is there for 8 hours a day)

The ore usually yields 1 blue gem per stack
I use the green gems to make the JC glass which yeilds a blue gem or a chance at an epic gem.
The primal earth i sell of 65-80g per stack of ten
Primal mana goes for 35-50g per
Primal fire is 35-60 per
Khorium bar -stack of 20 sells for 100+
Etern 1g per bar
The vendor loot usually rounds out to about 50-100g

So you really don't need to buy ore off the ah, plus you can buy 10 stacks of ore and run a streak where you only receive 2 blue gems from a 10 stacks of Adamantite ore. It is kinda of a crap shoot sometimes when you prospect ore. I have gotten a blue gem off of every prospect for 5 stacks of ore and there were times where I only received 1 blue gem every 5 prospecting turns. But you are correct Jcing is very profitable.