If you toss crafting out the window, then yes, inflation doesn't hit you, because while leveling there is nothing on the AH that you NEED, and passive money gains (dropped loot, quest rewards) makes up for your passive money losses (travel, repair, possibly food/water).

Just for one example, tailoring. Between auction house prices and accelerated leveling, you have to work very hard to create gear you would want to use as you level up. Tailoring eats cloth and spits out no desired (sellable) products until you get near the maximum ability. The value while leveling is largely in "using what you make". Which is highly difficult to choreograph in today's WoW environment.

A tailor can sell their cloth for large amounts to people leveling up alts, sure. But they do so only by cannibalizing their own progress.

Oh, and Tailor/Enchanter is recognized as one of the viable crafting skill combos, with the tailor providing the enchanting materials. They may be able to recoup some of their money selling unused enchanting material, but they don't have the other money making methods you're suggesting.