Why the huge difference in costs..? International shipping..?
I assume you mean in Brazil? Books and very expensive in Chile, compared to other things. And I believe it's because they are heavily taxed. I don't know about magazines, though.
To be honest, I'm not sure. VAT here is 19%, so if you are assessed duties on things you bring, you'll often pay that rate. However, I don't know what the rates are like for merchants importhing goods for sale.