We looked around for a cheap way to get our Prado and Tvan from Sydney to Perth recently and couldn't find anything economical.
The car wasn't too bad - $1200-$1500 from memory. The Tvan was more like $2500. I couldn't find anyone who would take them together - they wanted to send them separately and so the Tvan was a hassle because it didn't have a "motor". Some people were going to put it on a truck, some in a container and then by sea.
Loading the camper trailer should be ok because they don't need to get into it. I think the issue with loaded cars is you may claim they have stolen something at the other end and they have no way of proving they didn't - easier for them to force you to have it empty.
I gather Perth-Sydney is cheaper because most of the road freight goes the other way so people are looking for a load back.
We ended up getting some friends to take it to Perth for us - they are almost there. You have to be happy entrusting your vehicle to someone else and there is a risk they will have an accident but we decided it was worth the risk. They lent us their BT-50 and I had an accident in it on the weekend (reversed into someone because I find it really hard to see out the back) so the risk goes both ways
Another possible starting point might be Alice Springs - I'm flying our family back from there and got Qantas Frequent Flyer tickets cheaply (18k pts x $50 taxes per person). From there you can go up the Tanami Track to Halls Creek/Bungle Bungles and onwards to the Kimberley. Alice is a bit closer to Sydney - you could drive back in 3 days if pushed.