Brass: Once fired brass for .223 is roughly 8 to 10 cents whereas once fired brass for 7-08 is roughly 20 to 30 cents.
Primer: essentially the same cost (roughly 3 to 4 cents)
Powder:
.223 very roughly 25 grains, 10 cents per round
7-08 very roughly 40 grains, about 16 cents per round
(surplus powders would decrease those costs)
bullets
depends a lot on what you shoot, but for plinking:
.223: roughly 12 to 25 cents each
7-08: roughly 20 to 30 cents each
(obviously, cast bullets would be cheaper)
This gives you some ballpark numbers.
Have fun!