Some of the issues may come from their suppliers and their abilities to get materials. If a supplier can't get them the materials they need to make the things....what can they do?
Yes magazines are such simple things, but there are alot of things that go on behind the scenes in the industrial world. I have heard brass mfg's will only run certain sizes of brass for so many months of the year. If the supply runs out before the next run on those sizes you are pretty out of luck til the next time around. I would not be surprised if part makers ran in a similiar fashion, only making full size mag 9mm followers this month, compact size mag .40 followers next month, and so on.
The machinery to make the magazine and all of their parts are only capable of so much. Just buy new machines then right? Some companies did after the last big scare in 08/09, but keep in mind...machinery is not cheap, floor space may be limited or non-existant. I know when we have had to order new metal saws at work, we were told 15-18 week lead time til they would be delivered. Its not like walking into Walmart and buying a DVD, this is specialized equipment and as such is generally not readily available. Expecting companies to invest heavily to make magazines that could be banned a year from now is just plain crazy. Say everything dies down without a ban, eventually sales will go back to a much lower rate. They would need the mag sales to remain high to get their return on investment. On the other hand if a ban does happen, how many people are gonna start stockpiling those shiny new 10 rounders...enough to help that company recoup the cost of adding new equipment to keep up with the temporary high demand for hi cap mags?
Do you really think they aren't trying to get new units out the door. They know right now there is a PILE of cash to be had to whoever can supply the market. Even if they do manage to put out thousands of mags each day, there are how many people looking to purchase those up. Thats not including the people who are buying up everything they can just to mark up the price and re-sell.
Nobody could have foreseen the tragedies leading up to all this madness. As far as the gun companies, mag companies were concerned it was business as usual up til that point, their production levels were keeping up with demand. Sure had they known demand was going to take off they could have built up huge inventories....but nobody saw this coming. When/if this madness dies down and store shelves are stocked again, just remember how much it sucked when you couldn't find anything. Start buying things then, tuck them away someplace warm, and the next time some scare comes along you won't be paying $75 for a Pmag and $1+ per round of .223.