Securing is not the same thing as buying.
Example from my industry, electronics. I'm working on a project and need to source parts. I request a number of components from a company at my target price. They accept, decline, or make a comeback offer. If they accept, my quote will be good for a specified time frame. It may be as long as two years or even more.
This does not mean I bought the parts. In the meantime, I will secure quotes for the rest of the components I need for the project, as well as quotes for the pcb manufacture. I will not purchase until I have secured everything I need to complete the project. And if my client backs out in the meantime, no sweat. I haven't actually purchased anything. If the project goes through, I still don't necessarily buy all the parts at once. I may have secured a large number of parts in anticipation of future demand for the finished product. If it's a flop, only part of that quote may ever get filled.
Imagine if Apple had to actually purchase a million of every single iPhone component upfront, before even bringing the iPhone to market. No, they get quotes up front so they know what that cost will be if and when, and that they won't get screwed when there's no prearranged price and/or supply, and their whole business depends on certain critical parts. The one company making X could up their price, arbitrarily.
Gone to hoarders everyone.
Oh when will they ever learn? Oh when will they....ever learn.
Maybe DHS has simply outhoarded the hoarders in anticipation of Obama's second term? Their bid guarantees they get first dibs at the prepanic price. The price of our ammo goes up astronomically, because of the election that everyone saw coming. Added to the fact that the manufacturers have to set aside 450 million rounds a year (or w/e the number is)... just in case DHS decides to buy those rounds.... which further reduces the current supply until the manufacturers build up a big enough reserve of inventory and/or ramp up production sufficiently to ensure the DHS contract can be met if acted upon.
If you think about it, the more overpriced ammo you buy right now, the better the deal DHS has made for itself. You're increasing the value of their options. So if you're all up in arms about DHS "buying" all this ammo, then your best path is to wait it out and shoot less!