I know it is "immoral" to devalue packages, so
usually I do not do that unless the person
directly asks and even THEN I may or may not agree
depending on the circumstances.
One time I had a buyer who wanted insurance, but
yet wanted me to devalue the package to $20 (he
paid $150 for it).  It can't work both ways.  Of
course, he gave me every single curse word in the
Philippine (and English) language when he had to
pay $60 customs, but that really is not any of my
concern on a country's duties tax.

ANYWAY, just do it at your own discretion.  Don't
completely devalue a package (e.g. Package
actually worth $200, but you put $20 on the
customs).  The buyer should know what they are
getting themselves into before buying Internationally.

JC