Of course, it all depends on the age of the burial. Native Americans
used to trade. There has been flint heads found in the Southern Ohio
region with burials dating back some 2500 years. And the closest flint
to be found naturally is, I am told, in North Carolina. That's back
before they knew they were Native Americans.
        I think that traded goods may have been thought to have been quite
valuable, and thus would have been buried with a loved or respected one.
We still think the same way noting that many "Imported" goods carry a
premium.
        Art