This just seems too vague to me. I know it is extremely difficult to trace and control the provenance of every component, but from reading their statement, I kind of suspect the costs break down something along these lines (this is purely hypothetical):
Shoe- $10 cost to NB.
$2 - Research and Development in US
$2 - Intellectual Property, Legal, etc in US
$2 - Marketing/Sales in US
$1 - Management/ other workforce in US
$3 - Manufacturing/ materials...