The idea is to level through cooking with a repeatable quest, and you buy the mats of the AH. I'm playing on high pop realms, and there were barely enough mats to provide the 3x guys I took to 90. Took me roughly 40k gold in total and a good 10 hours while watching DVDs and doing other stuff.

Not gonna repeat the whole explanation here, since this comment on wowhead contains the info you need.