I live in Thailand and the duty can be handled several ways. If the item is shipped Fedex/DHL, UPS it might be included in the final invoice when shipping and the charge is very high. But frequently the customer has to pay for the duty in Thailand before the item is delivered. Unfortunately while there are set fees for duty it is very rarely followed and the amount charged is up to the duty officer. Sometimes a price can be negotiated. If a package is shipped via the post office and the stated value is not over a certain amount frequently no duty is charged. I think this problem is common in third world countries and we have to want something very badly before we would order it.
When shipping to somewhere like Australia, UK, etc you can probably contact the customs department of your country and find out the charges.