I sent stuffs form here a few times. I never got caught and my friends also never. I guess if it's from Europe, then it's less "risky" than from US mung ka.
Anyway, it depends on the intention of the seller ka. If she or he knows that there's gonna be an extra charge form the custom and doesn't tell u, then she should pay for that. But if she doesn't know, then i guess she should pay for the tax anyway but may be half...umm nun is na
if it were me, then i will help paying the tax a bit...just in case if the seller is nice to me in the first place na ka...