Here is what your forgetting it's the actual manufacturer or the source of where you are buying from who decides the value of what the phone will be going at. If they list $200USD then youshop will have to abide as they have no right to adjust the value on it's net worth so really it's up to the company to decide. With that being said I think no customs/fees will haveto be paid agreed bigmal?
Customs aren't that stupid. If they suspect a product has been declared below value to avoid gst and duty then they will charge as required and potentially fine or imprison (though I doubt you'd go to prison over a phone :-)
See page 14 of this thread http://www.geekzone.co.nz/forums.asp?forumid=48&topicid=109104&page_no=14
and this statement from the customs website.
"There are heavy penalties for concealing dutiable goods from Customs and for making false declarations.When purchasing expensive items overseas, such as jewellery and electronic equipment, you may be offered a false receipt showing a lower purchase price. This is intended as a way to reduce Customs charges. Do not succumb to these temptations.
Concealment of dutiable goods and the presentation of false documentation are serious offences which may result in the seizure of the articles and substantial penalties. You may also be criminally prosecuted."
Each to their own but I wouldn't do it.