Lets break this down.
Powder. 1 lb of powder equals 7000 grs. So divide 7000 by the number of grs in your reload. Then divide the cost of a lb of powder by the number you got from before. Ex 7000 divided by 20 = 350. Cost of powder 29.49 divided by 350 = .084257142, rounded to .084. That's your cost per round.
Primers, $32.99 for a box of 1000. 0.033 each. Used this for each reload below.
.223 AR 15
.223 69gr Sierra Matchking bullets $29.99 box of 100. $.299 each.
Powder, AR Comp. $29.49lb. 7000gr per lb. 20gr per round. $.084 per round
Primer $.033 + bullet $.299, + powder $.084 = $0.416 per round.
45 ACP
45 230 gr round nose bullet. I cast my own. Free.
Powder, Unique. $23.99 lb. 7000 gr per lb. 5 gr per round. $.017 per round.
Primer $.033 + powder $.017 + bullet free = $0.05 per round.
.338 Lapua Magnum
.338 300gr Sierra Matchking bullets $47.99 for a box of 50. $.960 each.
Powder. RL26. $28.49 lb. 7000gr per lb. 100gr per round. $.40
Primer $.033 + bullet $.960 + powder $.40 = $1.39 per round.