At even 100 rds a month of just 357, I'd say it's worth it. Factory 357 ammo is upwards of $30.00 a box of 50, around here. That's perhaps $600.00 for 1000 rds, which would represent a ten month supply.
Cast bullets at $70.00 per 1k plus $7.00 shipping = $77.00
primers $30.00 per 1k at your LGS
powder = 1 pound of Unique at $20.00 at your LGS
Total cost is just $127.00 for 1000 rds.
For jacketed, add another $50.00 or so.
You can buy everything you need to reload 357 for under $300.00. So you could save money inside of a year, very easily. But more likely you get carried away and end up with more components, dies, and equipment rather than cash in your pocket. It's easy to get carried away. But even if you don't like it, you will get to try it basically for free, after you make that first 1k bullets, which you can do in one or two weekends of free time.
What I can't justify is the time and expense for casting bullets. I'd rather buy them and spend my extra time on other things, like leatherworking.
Have you ever tried it? Time: casting bullets is very fast. Tumble lubing is very fast. Sizing, typically optional, most of the time. Expense: the initial investment is very small. A Lee bullet mold is only $20.00, and beyond that all you need is something to melt and pour the lead; that's another 40-70 bucks to get a nice setup, if you don't have already have the cookware to spare. And then, even if you buy ingots delivered to your door, you can cut your bullet cost in half for common calibers. By several fold, if you have a less common caliber. So don't even worry about scrounging lead; that's just a big fat bonus if you can get free lead. For your time and money, casting is easily the most rewarding part of reloading. It's so easy, a monkey could do it.