Most of the insulators that I buy and sell are in the $200 or less range. I have insured shipments for up to $400 using previous described packing methods. If I were to send a $600 or more insulator I would take special precautions. A box within a box is about the best method I can think of. One precaution I would also take is to not ship a cheap insulator with an expensive insulator. It could become the hammer to the expensive insulator.