It is not a huge discount (5-8%) but they generally have good prices anyway, it is nice to get free shipping without buying a case (you can buy smaller quantities of ammo without killing discounts on shipping), and they stock a wide variety of calibers and brands. It has been worth it to me.
But it still isn’t the only place I order ammo from - sometimes another place has a better loss-lead price. And certain calibers (6.5C, 7.62x39) are under represented. Always worth shopping!