The manufacturers are pounding them out. Magpul had a backorder of over 1 million Pmags almost overnight after Sandy Hook, it takes a while to deal with a spike like that. The buying frenzy in the US has already cooled off noticeably and things will recover , but it is still going to be 6 months or more before anything like normal levels of stock start being seen again. The frenzy stripped the entire supply chain bare, that leaves a big hole for the manufacturers to fill back in.
Mark