The Onion wrote this as a joke, but it’s closer to reality than they probably know (since no one who works there has probably every been in the military).
When I was in the army we’d get magazines in the office advertising items like tactical missile packages, self-propelled artillery and anti-aircraft radar and weapons. Nearly anything in the modern arsenal at one point or another I saw advertising for.
It’s not that units (usually) purchase such items themselves — but the decision-makers in line units do influence people who can and do make purchases, both directly and indirectly. So the arms manufacturers logically advertise to those influencers. And of course it’s not like you can walk down to the corner missile store and buy these items, but like all things in a capitalist society they get purchased — and that means advertising.
The first time I saw an ad for a cruise missile in a magazine I was looking at, it kind of blew my mind a little. But then like most things I just got used to seeing ads for automatic grenade launchers and howitzers next to whatever article I happened to be reading.