Was gonna say exactly the same. Mostly don't get insurance because all of it is all but a scam. For shipping expensive items, pay for faster. ALWAYS Priority, and faster yet if you can. You get tracking and just generally the speed reduces the chances for screwups. Fast shipping rarely goes to the next state by way of Alaska, Guam, and PR. It just goes straight there.
Yes for mailing I normally buy insurance for sales so buyer thinks we're covered.
But yes also as advised, complain more. Maybe even to get your lawyer (assuming one already on retainer, you are a business...) to write a letter to them. Remember they are not just evil, but CHEAP. They want to get out the cheapest they can. Automated denials (or a few minutes of a minimum wage worker taking your abuse) is cheap compared to writing a $1,500 check. But you get a letter implying you are taking this seriously, they may cut their losses, relent immediately.
