Dunno what you mean by cheap but there are less expensive ways
try www.e-go.com.au
I've used 'em for bulky stuff before, slow but they haven't broken anything yet. Depot-to-depot brings the cost down a fair bit.
Have also sent bulky freight depot-to-depot via greyhound bus. They might take a smaller SUP
Contact Australian Air Express. Drop off and pick up from airport. Quick and cheap for surfboards etc. it'll depend on if you are sending a surf or race bOard I reckon.
Worth a call!
DM
Buy your self a ticket on Virgin Blue and pay the $20 for 40kg excess baggage and go for a trip!!!!!!!