It's really the "perfect storm."
1. No doubt there was increased consumer demand for a number of reasons.
2. No one can explain exactly why the Czech, Russian, and Italian manufacturers did not step in to fill the insatiable American appetite for ammo. There is no Obama in Italy. There is no military rerouting of brass in Serbia. They just didn't do it. They left money on the table. Perhaps the exchange rate of the dollar wasn't worth the small margins on ammo, when weighed against the labor cost of ramping up production.
3. Despite what you may have heard, the big three American ammo makers did very little to up their production. This was a myth. They didn't really make any significant changes until March, when they finally began stamping 9mm at a higher pace to satisfy angry wholesalers and retailers.
Find an interview with an ammo manufacturer in an enthusiast magazine. The NRA has four hours of satellite radio every day. Find the podcast from their interview with Remington. Winchester. Find a press release from an American ammo manufacturer which says "Hey, we know there's a problem. We're working on it."
You can't. Why?
Keep in mind this strategy didn't make The Big Three any richer. They weren't selling to retailers and wholesalers at a higher cost. Wal-mart, Bass Pro, *****, Cabelas and Sports Authority still had the same ammo at the same price as always.
It was the Mom and Pop gun shops who tacked on the 3x screw charges.
4. For a variety of reasons, at the same time the Military changed it's policy on brass and panic buying set in, there were no primers to be found for those who press their own ammo. Serious shooters and hard core enthusiasts who would have normally not factored into the frenzy found themselves competing with Johnny-come-latelys like me.
It's mostly over now. Mostly. Retailers ha've stopped rationing everything in my midwestern town except .25 and .380. There are thousands of boxes of 9 on the shelves of the Cabela's next door to me.
More profit in 9 mm and 40 than cheap-o .380 and .25, so little bullets are last on the priority for ammo manufacturers.