I presume you got the ticklet from the USA Site (airnewzealand.com) and not the NZ site (airnz.co.nz) as business saver don't exist on the NZ Site? (or I may be wrong)
http://www.airnewzealand.com/tasman-...cific-business
http://www.airnewzealand.com/business-fare-conditions
Business Saver: Before departure, refundable less $500 cancellation fee or $150 charge for no show and no money back or am I reading it wrong?
Where are you seeing the $300.. I see $500 fee