Does anyone have any personal knowledge, info, or experience in transporting
more than $10k worth of precious metals through TSA, and customs, although
this would be a domestic flight?
...
Many years ago when I still had money to invest, I bought $10,000 in
gold coins. They were mailed to me at a post office where I picked
them up. I was impressed at the time by how little it cost to make
the delivery. I mailed the coins to a buyer at a later date and was
very impressed by the cost of mailing and insuring the coins. The
company that shipped the coins to me obviously had a blanket policy to
cover any lost packages they mailed.

Send your valuables by mail, disclose the contents to the post office,
and pay for full insurance coverage.