Just gone through this for insurance.
The quote to transport from Darwin to Sydney was over $1800 one way.
I would be guessing you would be looking closer to 2k. A lot of boat transport companies will transport trailers as well. Be careful though on how they load them. when mine arrived in Sydney the handbrake cable was severred apparently by the use of a forklift. The camper company said this was normal type of damage from campers been transported.
Towing it might be the better option if you have the time.
Best of luck.
Cheers, Chris