I just priced out all my components.
Bag of shot 25 Pounds $85
Pyrodex 1 - pound $24
Wads (card, fiber and over) total 1000 each $38.07
70 grains load powder and 1 oz. of shot, 1 of each card per load.
25- Shots = $5.30 in shot (Magnum Lead); $6 in powder and $0.95 in wads.
$12.25 per 25-shots or $.049 each shot.
If you reduce the amount of shot to 7/8 oz. the price per 25-shots goes down to $4.24. Using the square load, the cost of powder goes down to $4.80. The total per 25-shots is now $9.13
You guys that say you can get shot for $50 per 25- pounds would only spend $3.12 in shot for a total of $10.07 for twenty five 1-ounce loads and $2.58 in shot for a total of $8.33 for twenty five 7/8 oz. loads.
If you made your own wads from scrap material you'd save just about a buck per 25-rounds.
The cheapest conventional 7/8 oz. loaded cartridges on-line are $7.99 and the better quality 1-oz. loaded cartridges are $11.99 per 25-round box. This is on-par with the cost of shooting a muzzleloading shotgun.
You left out caps/flint cost.