Have you ever tried doing this on a lathe? You'd still need some sort of press to get the tapered shape, but ignoring the expense and the need for a press anyway to get anything except straight sided pistol cartridges, think of how long it would take. I just made some stainless steel repair parts about the size of a .44 cartridge on a lathe, parts that didn't need the precision that ammunition needs and didn't have to be tapered (replacing a broken aluminum boat hatch hinge - no longer available), and making half a dozen of them took all day.
What you’re missing is that you can also make your own tooling.
Get some O-1 drill rod, and start from there. Learn how to heat treat and temper steel, and you’ll have to worry about your final dimensions once. After that, you just keep using the forming tools.
I could, in theory, turn a chamber for a rifle on a lathe with a boring bar. But that takes too long, so we use reamers that are sized for the chamber in question.
Custom made tooling is the cat’s ass. That’s why I have a collection of O-1, A-2 and S-7 drill rod next to my machines. Need a screwdriver, punch, chisel, cutter, drill bit, countersink, whatever? I make it, then heat treat, temper, put a little grind on it and wha-la. I’m off to the races.
Seriously, check it out. Saves you GOBS of time...