I picked up two boxes of Winchester .380 at the gun show for $17/ea.
BUT AmmoEngine is showing, Cheaper than Dirt and Sportsman's guide all have several selections of .380 for under $30/100
Of course shipping may nix the deals.
I'm gradually building up my .380 brass collection. When I hit 500 hundred, then I'll start reloading. But I'm only netting about 10 rounds a week at the range, so it will take a while.