The spike in popularity of .380 "mouse guns" over the last couple of years has driven up the prices of those guns AND the ammo that goes with them. Before that, like you mentioned, .380 ammo was relatively higher in cost than its bretheren, but not like it is now.
I wouldn't even attempt to buy any factory ammo for this caliber, if available, due to the insane prices retailers are asking.
Thank goodness I, inadvertently, accumulated a small cache of .380 brass and factory ammo before all this panic buying started. I think I paid about $12 per 100 count of Starline .380 brass from Midway (sale price) plus a 500 count box of Miwall (gun show ammo) factory new ammo for $27, all prior to the anticipation of the coming obama regime.