an "oh crap" moment

So, I've started listening to Writing Excuses (as I may have said), and I was just listening to an episode from their first season where they talk about costs of magic.

AND.
MY.
JAW.
DROPPED.
OPEN.

I've been pretty proud of my NaNo Novel (here after called Wielding the Locket (Here after referred to as WtL)). I mean, I still have a lot of work to do, but the frame work was there. and the more I add and edit, the more excited and proud I get.

I forgot the books. (Ted Mosbey from how I met your mother tells a story of an architect that built a library but forgot to account for the books, the building sank a little each year and was eventually condemned.

I wanted my magic system to be available to anyone willing to learn, I wanted a years worth of learning to be be a solid start. a year to learn a lifetime to master, sort of thing. The magic system has no health costs (beyond some fatigue, which is cliche) and has no moral cost. the cost is generally in material, time, and the distance of the magic user (wielder) from the affected area. There's other potential costs, but you could get by with just those for the most part. There's also increased random activity surrounding magical activity. I'm actually fairly okay with the cost of the magic. although, I need to do something about the fatigue, it's too cliche.

the problem is, Magic has almost no effect on my world's economy.  why wouldn't everyone learn magic to aid them in their every day life? I do have rules set up about being approved as a "student". But there's a large number of people who can wield. Why aren't they making big bucks? well, some are, but why not more?
With the limited number of wielders, why aren't there people training an army of wielders to take over the world?

I haven't thought of any of these things, it very well may be my story's Unmaker.

Bed Time, maybe I'll find another puzzle piece or two that will answer these questions and unify the story even better, while I sleep.