Shipping through the USPS

I shipped an old (but still valuable) camera off to have something modified - the post office destroyed the box and damaged the camera.
I had insured it. There is no way to talk to someone to say "hey, let's get a repair estimate and see what it's going to take to fix this".
So I filled out the form and asked for the amount it was insured for.
Had to take the packaging and damaged camera to the post office...in Decatur, GA (I'm in Phoenix).
Had to pay someone's time on the other end to go to the post office...they've had my camera since mid April.
They rejected my claim - I hadn't provided sufficient proof of value.

I called - they told me I had to appeal in writing - no way to get a decision maker on the phone.
I appealed the decision and sent more information substantiating my claim.
They denied the appeal - insufficient proof of value.

Sent in a second appeal - I sent exactly what they said would be sufficient proof of value, and said, "either ship it to this camera repair place for a repair estimate, or pay me".
Second appeal denied - 'insufficient proof of value'.
They've had $1500 worth of camera gear for 3 months now.
They get 30 more days to respond every time I send them anything.
Nobody capable of having an adult conversation can be reached by phone
I jump through all the hoops, and they just keep denying the claim.
Your only hope seems to be having a receipt for having purchased it recently (even though they say a statement of value by a reputable dealer will work - denied twice).

FedEx for me from now on.
And I hope Amazon runs the USPS into insolvency