The weaponlights are issued "as is" to the troops...much like rain-gear, cold weather gear, etc. Once they issue it to you, they count it as an expenditure...most of the lights are in to rough a shape to be re-issued...so, instead of paying some-one 70-80-g's a year, they give the soldiers, that require them, the light for there weapon before they deploy...and they're expected to USE IT...if they have it for there second tour, so be it. They get back, they're done with Iraq, and decide not to re-enlist, they have all this cool "gear" that they realize is worth something...
I'm in the AF, and I have about 3k-4k worth of gear (some new, some used) that will never see the light of day if I don't use it. But, me being the "survival type", I'll hold onto it...just in case...
Flashlights are just like underwear...once they issue it to you, they don't wan't it back...and keep in mind, while these weaponlights might seem expensive to us, compared to the $2k body armour, $500 helmet, etc., al., it's a drop in the bucket for them. Wasteful? Maybe...but, that's part of what the military industrial complex was designed to do...support American companies, and so forth. Uncle Sam get's it back eventually.