That line about "thought those $12 insert holders were junk" is exactly what I used to say too. I watched a guy on YouTube run a whole batch of aluminum parts with the cheap holders and he said the trick is making sure your insert sits flat and your torque is right, because most of the bad reviews come from people who crank them down uneven. He also said the set screws that come with them are soft, so swap those out for better ones and you get way more life out of the holder. Makes sense why yours held up for 400 parts when a lot of folks give up after one cut. Price does not always tell you how well a tool works, it just tells you how much the brand spent on marketing. Glad you gave it a real shot instead of tossing it in the trash like most people would.