To determine a price to get started is tricky, as there is lots of second hand kit about. So let's pretend we have won the lottery and will be buying everything brand spanking new! Basically the worst case scenario...
Beginner Package (Board and 12m Kite): $2,000
Public Liability Insurance through WAKSA memberhip: $120
Buy second hand and you can easily get setup for under $1,500 with everything!
Become friends with a Kitesurfer and it could cost you nothing!
There are many kitesurfing shops in Western Australia, or you can look for second hand gear on Seabreeze and eBay.