Inscription is the newest profession in World of Warcraft. What's the cheapest way to level inscription in world of warcraft?
Regardless of which guide you follow, the cheapest way when only looking at
Using your favourite
That doesn't mean it is the fastest but that would be the cheapest way as it costs you no gold.
However, there is an argument whereby
But that is another whole topic in it's own I think.
http://www.elsprofessions.com/inscription/leveling.html provides the best levelling guide for Inscription.