Shotgun shells are priced by the box.  We have 12, 20, 410, and some 16 gage.  Also look at the shotgun shell length, shot size and the dram equivalent.  There is a lesser price per box when you purchase a case of 10 boxes.  Most shotgun shells have 25 shotgun shells per box.  Some special shotgun shells will only have five shells such as slugs or a particular buckshot.  Bismuth have ten shells per box.  We have trap and game loads, lead and steel shot.  I have taken pictures of the ends of the boxes and the cases for the specs on each.