I haven't gotten into reloading yet, but I hope to some day.
When you factor in the time, you'll find out that the expense will dramatically increase. The questions, then, become:
1. How much is your time worth.
2. How much time does it take to produce your product.
"Worth" is relative and is based on a lot of things. For example, one could use your regular hourly wage as an indicator of how much your time is worth.
Let's say, for example, that my hourly wage works out to $60/hr as an engineer. That's a dollar a minute.
How much is my time worth when making ammunition? Let's only figure time and assume that the cost of material is already a done deal (you have lots of stock on hand which you've built up.)
Well, I can buy a bulk case of 9mm 115 gr FMJ Blazer for $200 right now. That works out to $10/box for 50 rounds. Using this, I could say "if I can produce 50 rounds of ammunition every 10 minutes, then this is worth my time" because it would take me 10 minutes to earn the $10 I would need to simply buy that box. At 10 minutes per box, it would require me 200 minutes, or 3 hours and 20 minutes to generate a case of 1,000 rounds that I could buy for $200.
So, that's one way.
But the relative worth of your time is not just based on what your time is worth as an engineer. If you have to spend 3 hours and 20 minutes to make that case of ammunition, you now have 3 hours and 20 minutes less time to do things like the yardwork that needs to be done, go on that fishing trip, play games with your kids, knock boots with your wife, garage time to change the brakes on your car, etc.
So worth is always a balance of things you value.
If you are on a tight budget, then perhaps saving that $200 in cash means putting in the time to make that ammunition to support your shooting hobbies is worth it, because the OTHER things you need that money for mean more. Like paying rent, keeping the electricity on, or saving up for your 10th anniversary trip with your wife.
In this case, you judge that the time it takes to save that $200 is well worth the effort.
So this isn't strictly a matter of "savings"...it's a balance of "worth", and that's not always strictly a matter of dollar signs. Worth is based on a lot of things...how much your time is valued, the things you learn from the things you do, the enjoyment you get out of doing something, the sense of pride one has for a job well done, the value another places in something that you personally had a hand in creating, etc. Ask any woman, for example, what she values more: A bouquet of flowers you bought at the grocery store floral section, or a bouquet of flowers that were hand picked and arranged in a vase someone took the time to find/make based on colors/patterns she likes.
The same principles apply here.
We do this with most everything we do. So I can't imagine this would be any different.