+1 lawnboy and Techno.
Here's my interpretation of the history of ammo prices for the last 15 years or so.
Ammo prices were depressed in the 1990s by a combination of the end of Cold War-level NATO procurements freeing up Western arms factories, rapidly falling commodity prices, and the sudden availability of additional supply from the former Eastern Bloc countries. This was a "perfect storm" that pushed prices lower than they had been in decades, and we probably won't see that combination of market factors coincide again.
Prices rose through the early 2000s as commodity prices rose on optimism that the Asian (particularly Chinese) economic boom would continue. The rise in commodity prices had little or nothing to do with ammo specifically; it was prompted by forecasts of continuing greater demand for consumer products in Asia.
Ammo prices should have fallen when the economy tanked in 2008-2009 and commodity prices fell, but post-election panic buying propped them up into 2010. When people are buying everything that comes in the door within minutes of its arrival, there's no incentive for retailers or wholesalers to lower prices.
In 2011, prices fell due to continuing low commodity prices, a glut at retailers who had ordered too much ammo late in the panic, and the fact that some buyers had stockpiles large enough to last them through the year and weren't buying more.
In 2012, the market has stabilized enough that retailers feel confident raising prices slightly, partially in response to generalized inflation. Some retailers may also be hoping for a second election-year panic.
Ammo prices are still fairly low compared to historic prices from the 1930s to the 1970s.
