See my post above DaveR.
Shot cups used are the same as those used for hunting heavy field loads. Sometimes they are the same as those used in trap/skeet loads. You can buy more expensive wads from places like Precision Reloading, but the reloading costs approach that of factory ammo.
Buckshot requires a much slower burning powder due to the payload weight,which necessitates increased charge, which in turn, increases the per shell unit cost.
I reload OO in 9 and 12 ct,OOO in 6 and 8 ct.,and #4 in indeterminate loads. I use Hornady buckshot, but am on the lookout for bulk Winchester OO buck as a more economical approach to Hornady's $8.95 per 5 lbs buckshot.