I heard of a local bowler who has KMT and when I first of this, he was drilling for himself only. Few years later, I heard he drills for two other people, friends of his.
I think this a good Idea, cost is much much much lower than a mill, especially if you're just drilling for yourself.
If bought 3 to 4 balls a year, I would buy myself one. Or drill for friends, but they buy their own plates.