If it's a gift, and the value is less that $100
then the customs section
of the
US embassy pages here in the UK imply that there is no duty to pay -
other than that the first $100 would not be subject to duty.
The problem is if customs things the value is more than $100.
If you buy it for $25, the value is $25, and it doesn't matter what
customs thinks it is worth.