In looking at the U.S. Custom's web site, they specify that items for personal use are subject to an $800 exemption. Then they give the rates for other items above and beyond that. What they don't make clear though is for non-personal items, things for sale/business, what the rates are for the duty. Does anyone know? Is there a special form she should have with her before arriving?
And the idea of saying they are for personal use isn't going to work... 100 plastic lenses are clearly not for personal use

-Tony