As many people have pointed out, leveling JC will cost thousands of gold. The cost will be the same whether you mine the materials yourself or happen to find them dirt cheap in the AH.Originally Posted by Herros
You should realize that all the advice given in this thread (level a miner, do dailies, buy underpriced stuff from the AH) are actually just generic ways of earning those thousands of gold and not linked with leveling JC in particular. Therefore you should think about all the money making tools that are available to you (be creative), calculate the highest gold/hour activity and grind that until you make the 4-5kg that leveling JC will cost.
For example, one advice was to look for very cheap gems in the AH. However, why should you limit yourself to looking for cheap gems in particular when you could just as well be looking for any items that are underpriced, re-list them, and use the profits to buy gems? This advice is the same as "play the AH to make gold", except it's worse since it's telling you to limit your profit opportunities to just gems.
Another popular advice is to level a miner. For this you have to calculate how many hours of playtime it will take from character creation to the point where you have collected all the materials. Then calculate the total AH value of all those materials and divide by the total time it took to collect them. If that value is less than the gold/hour of doing dailies, for example, then you should do dailies instead. (Although your mining character will have residual value even after you have maxed JC which you might want to take into account.)
Typically the highest gold/hour activity will be available on your main since it will be better geared and have faster mounts opening gold making opportunities that you can't get on less developed alts. This is the reason why leveling a mining alt is probably not a good idea; in the time it takes to collect all the mats on your alt, you could've grinded enough gold on your main to buy the mats from the AH and have a pile left over too.