weera2500: Apparently I am not the only one...there seems to be quite a few users caught out by their hidden costs.
A little clarification is needed here. They are not "their" hidden costs. They are costs passed on by customs in NZ who charge GST and/or duty on all imports where the value exceeds the de minimis value.
If you were not aware that importing goods into NZ meant you were liable for GST and/or duty I think you just need to flag it as a life experience rather than trying to blame anybody for it. I'm not sure what else customs can do to educate people about these charges, but as you were obviously unaware maybe you could offer them some advice on how they can help people.
You'd paid these charges to the NZ government, not Expansys. The only way you'll get your money back is to return the goods, and for you to lodge a claim with customs with proof from Expansys once they have received the goods.