Its prob best you submit the total number of purchase to the vendor to get a total cost inc shipping first (bearing in mind we the guy with different item may have different cost)?
Duty seems to be around 15% based on the below which looks like a major PITA paperwork:
http://www.customs.gov.au/site/page5549.asp#Above1000
People can make a decision to go ahead or not once we have clearer picture..