Aaron,
Shotgun takes a different press. These days the bulk / cheap wal-mart shells are about as cheap as you can reload. Difference is in the higher priced shells you can still see a savings. If you are a dedicated shotgunner you could purchase in bulk and see some savings. If reclaimed shot works for you then that would figure into your savings as well as using some of the cheaper shotgun powders.
Now when you start in on 16, 28 and 410 the savings increase as well as load selection for those three as well as for 20ga.
Same with shotgun and metallic - figure the cost of components in your area or in the volume you would order on-line and see if there is a savings. Many times you can find a couple of folks to go in on a shipment and save on shipping and hazmat, and might get a volume discount.