I had to replace a 3-step pulley on a machine -- the old one broke and had been replaced with the wrong one which was horrible. My choices were to make one or to buy one. I wound up buying a die cast one from Chicago Die Casting Co. even though I knew going in the runout would be terrible. It was. I put it on a mandrel and was able to true it up on the lathe, though, and now it looks and runs like a 100% lathe-turned step pulley. Only a couple of hours work instead of a couple of days, too, mostly fiddling with setups.
I've dissed these die cast pulleys before, but now I know they have enough pot metal in them so that they can be trued up. So, like many things nowadays, you have to regard them as "kits".