For the past 6 weeks, I've been helping folks in the "Ammo Finds" thread in the Rimfire forum at Calguns...giving heads ups like other members where to get ammo.
I've been able to acquire 7000 rounds of .22 LR over that period - while providing links. My average when broken down is in about the 9-10 cents per round range after shipping.
What the trick?
Keep about 13-14 windows open all day and all night on the browser to different vendors. And especially Sunday night into Monday morning - get ready to jump. Last week on Sunday night, I predicted a Monday flush. Sure enough starting Monday morning - about 6 vendors added 2-3 affordable each - and a bunch of us keep each other alerted and jumped on them same thing happened just the past Monday:
CCI in bulk containers and in 100 ct boxes.
Federal in bulk containers
Eley and Wolf in 50 ct boxes
Here's a list of the best vendors for me so far for you folks:
(CCI and Eagle)
(Aquila and Federal)
9mmammo, CheaperThanDirt, and BulkAmmo have gone "armslist" at this point. Don't bother anymore...