They offer a prime membership option, much like Amazon. Then all ammo, in any quantity, ships free and discounts are deeper. I enrolled and feel it is worth it. Needed two boxes of some fancy .243 last week, and got it postage-free in a couple of days, and much cheaper than any place local.
They also sometimes have ammo in stock at a great price, when I keep reading no-one can find any (elsewhere).
I use the Fed American Eagle for all my .380 practice.