That sounds fishy! There may be a glimmer bug, now that you mention it. I haven't noticed a drastic drain when I wasn't spending any, but you remind me that when I upgraded a weapon the other day it seemed to drain my glimmer a whole lot more than it should. I thought I just hadn't paid attention to my glimmer account and maybe didn't have as much as I thought before the upgrades.... But if there is a glimmer drain, somebody in the Tower is following the Office Space plan and draining our accounts. Specifics: I keep my glimmer between 20000 and 25000. Whenever it gets close to max I buy 5 heavy syntheses from the gunsmith to go back to 20k. I don't know if I was at 20 or higher, but after upgrading one legendary weapon my glimmer was at 9k. It doesn't cost 11k+ to unlock a legendary! Edit: as an epilogue, I didn't like the gun in the end and broke it down, so those were 5 very expensive legendary marks.