I once USPS shipped a gem to NYC Gem cutter to be re polished. It went registered, insured- the full monte. The Cutter returned it in the same way, fully insured and registered. The package got lost in a distribution center in a town a couple of miles away from me.
When I went to collect the insurance, the USPS was horrible. They demanded explanatory letters from me and the Gem Cutter and then demanded an official appraisal on the letterhead of a prominent, unassailable appraiser.
I provided everything they asked for in triplicate. They sent me a check for the value of the work performed by the cutter in NYC. When I balked at accepting this in lieu of the original insured amount, I had to fight with the Local Postmaster for resolution. For nine long months, I called the Postmaster every week and argued with him for at least an hour at a time. He eventually relented and issued the check for the original insured amount. I have learned that smaller high value items are best shipped via FedEx or UPS. I still use the USPS to send documents or low value packages, but avoid using them otherwise.