Shackleton, if you want to shoot a 45-70 on a budget, try 16 gr. of Unique with a 400-425 gr lead bullet. You will be amazed at how well this works, and in most rifles with good bores, it also very accurate. It give about 1250 FPS + or -, depending on barrel length.
Now a pound of unique would get 437 shots at 16 grains. At $21 a pound you'd have 4.8 cents in the powder per shot. If you cast your own bullets you can shoot pretty cheap. 4.8 cents for powder and 3 cents for a primer. If you can scrounge lead the bullets will be almost free. You do have to lube them, but that's so cheap that i bet there's not a penny per bullet. If you had to pay 40 cents a pound for lead you still get 17 shots per pound so that comes out to 2.4 cents per bullet.
Brass will last at least 15 shots if your chaber is good, and if you don't over bell or over crimp.
Steve