I called Borepatch last night to tell him about the surplus .303 at $0.40 a round. One of things I said was, "You can't reload it for that price." Which is true, if you're buying projectiles.
I looked up some prices. These are current prices, although the powder was unavailable.
Bullets -- $29.00 a hundred, so 29 cents each
Powder -- H4350, $28.00 a pound, 7000 gr./lb., 44 gr./round, so about 17 cents each
Primers -- $32.00 a thousand, so 3 cents each
Cases -- Let's say you have the cases.
Reloading .303 British would cost you $0.49 a round for materials. ($235.00 for 480 rounds)
Of course, you could cast bullets. Assuming that you can find a source of free lead and you don't count the cost of the propane to make the ingots, let's call the cast bullets free. Now, you're at 29 cents a round. ($139.00 for 480 rounds)
Let's also forget all the equipment costs for the reloading and casting equipment, too. Call that a sunk cost, amortized years ago. The storage and work space, tables, cabinets, presses, dies, the brass prep tools, scales, lead molds, lubrisizer, powder measures, etc. all written off and forgotten.
You haven't done the work yet. So let's talk about time.
Note**: The following applies to calibers you already know, that you have loaded before, and that you can readily set up. If you were starting with a new caliber, all bets are off on how long it would take. You would be making up small test lots, going out and shooting them over a chronograph and shooting them for accuracy and function, collecting data and generally spending many hours getting to the point where you would consider loading in larger quantities like this.
Say I set up the lead pot, get it heated up, warm up the mold, get all the safety gear on, and cast some bullets. I have a 2 cavity steel mold, and allowing a half hour of getting things ready, I start making usable bullets at the rate of 4 to 6 bullets a minute (I'm an optimist). Allowing for some futzing, some discards, and the setup time, I make about 200 bullets an hour for a couple of hours work.
I take my 400 usable bullets and run them one at a time through a lubrisizer to size, lube, and seat a gas check. That's probably 2 bullets a minute, give or take. Maybe I'm a little quicker than 2, so let's call that 3 hours at the lubrisizer.
That's 5 hours to make 400 loadable rifle bullets. And I think that's optimistic, but not unrealistic.
Now you tumble up 400+ cases. One by one, you rub some lube on them. I use Imperial, put a very light coat on each case. Get the sizing/decapping die adjusted in the press. Pick them up one by one and size them. Then maybe I tumble them again, or rub the lube off. After that, one by one, I prime them. I have a couple of priming tools, but none that don't require some attention and effort.
Primed, sized cases, ready to be loaded with powder, are what you want to keep around. Now you set up the seating die in the press. Set up a powder measure to the specified quantity. Then you put powder in cases. I tend to do 10 at a time, then check them visually. Each one is run through the press one more time. At this point, setting the bullet in place and pulling the handle finishes a usable round.
What kind of time do I have in making 400 rounds? 3-4 hours to lube and size the cases, 2-3 hours to prime them, 4-5 hours to throw powder and seat bullets? I dunno. I doubt I'm handling a hundred an hour on a single stage press no matter how efficient I am. I may have to actually time myself on each step of a hundred the next time I do 30.06 and see what it is for each part of the process.
Pretend I'm in the ballpark and it takes about 2 hours accumulated work to do 100 rounds of rifle ammo for a caliber you're familiar with. If you're using cast bullets, add another 2 hours to cast and lubrisize 100 bullets (one hour for each step).
What is an hour of your time worth? I reload. I cast. I do it because I enjoy it. It's a hobby unto itself, not just work I do so I can go enjoy the shooting sports. But I know I'm not reloading to save money and I don't think about the time.