The good news is that there're lots of commercial sources for "remanufactured" ammo with cast bullets in virtually all common handgun calibers.
The bad news is that they're often little if any cheaper than new generic ball in semi-auto calibers.
If you're looking to do a good deal of shooting with one specific caliber for the absolute low-buck, consider becoming a reloader. Commercially cast bullets can be had in quantity from local sources in most areas by checking out the shows and larger retail gun and reloading supply shops. Ditto brass, primers and powder. In most cases local sources are more economical in the longer run than most mail order outfits when you factor-in shipping and HazMat costs, IMO.
A basic progressive press outfit like a Dillon Square Deal B or Lee Pro-1000, a powder scale (balance or electronic), a dial or vernier calipher, and a manual will pay for themselves in less time than you'd imagine. I suggest a progressive because, once you've settled on a "standard" load, you can produce enough ammo to supply all of your practice or training needs with the least possible time and effort. An hour or so on a typical progressive press will crank out enough to fuel an average Saturday and then some.