Thanks for the suggestion, Bill. However, with the almost unlimited variations which I offer in my molds, EDM machining would be impractical. Also, it's only real advantage would be to cut heat treated steel alloys, as you have stated.
For a half dozen reasons, there is no better mold block mateial than aluminum. If the caster doesn't abuse them, LBT molds will cast precision bullets for a lifetime, and do it faster and with less effort than any other brand of mold. With some experiance, 400 bullets per hour with my two cavity and 800 bullets per hour with my four cavity molds can be expected, with very few rejects. That production rate cannot be even thought of with steel or iron blocks, or cheeply made aluminum.