I leveled Inscription on my DK when I hit 80, as I was leveling I heard a lot of bitching about Hodir dailies from guildies, and the other character I was leveling with the DK was an herbalist.

I bought the mats for vanilla WoW herbs off of the AH for ~1k used a ton of saved herbs for TBC (free for me) and then nabbed the stuff that my herbalist got leveling herbalism for the rest.

You can level it to shoulder enchant range for less than the cost of an epic flyer if you were buying it all. 3-5k gold.

It is a great money maker once you get some of the popular glyphs but it research is a ~75g daily investiment and doesn't really pay out for a couple months. Takes 83 days to get all of the glyphs.