how can I insure a shipment for more than $10,000

They mail diamonds all the time at the USPS. 

Guess I'd be focused on finding which either insurer or shipper actually stands behind the insurance if a claim needs to be filed; how the items needs to be packed and by whom with proof of such; what needs to be in place as proof of item and packaging condition prior to shipping, and what's required afterwards. Nothing is ever straightforward in these matters

I am not sure of your situation. But I have my dealer do everything, so I am never in a position of shipping anything like that. 

what is a dealer? That is only half joking.There are no high end dealers with 3-4 hours of me. Even if there were, I can't afford to buy what I want working with a dealer, so like most of us, wheel and deal on sites like this. 

and I'm talking about selling a used item I have, No dealer is going to help me do that.

I took it to Fedex. I don't know what the limit is , but they did go $19K. It looks like the 3rd party sites that offer discounted shipping have their own limits. The ones I am used to using cap it at $10K. 

all good... thanks