OK Mick, I'll be your slave. (ie the info is on the link on the original post but I have to work it out for myself anyway)

Fares

Adelaide to Darwin
- Gold Kangaroo A$1740 per person

(this is for a premier class cabin) (from Melb it is $1850)
- Red Kangaroo (ie basic level cabin) $1390 pp (Melb $1490)
- Daynighter seat $440 pp (Melb $490)

Vehicle up to 5.5 metres in length (no roof racks)
-Adel to Alice Springs $389
- Melb to AS $439
- AS to Darwin $449
ie $1676 return for vehicle (Adel) and $1776 (Melb)
These rates assume you are travelling on the train with rates obtainable by quotation for unaccompanied vehicles.

So if return journey
if 2x persons using Red 'Roo accom with one vehicle A$7236
if Daynighter A$3436
Add $500 for Melb Red 'Roo or $300 Daynighter seat.

The journey is for 47 hours !!!! and 2979 kms.

Defintiely not cheap.

On the other hand a journey from Adeladie (return) is at least 6000 kms (probably more) if say 25 mpg and ave $1.10 per litre (probabaly too low for the outback) fuel would be $750 plus if you manage 1000 kms a day it would take three days good driving one way (plus the Melb leg). Say four days from experience at least. Plus wear and tear on the vehicles.

If flying obviously it would be balanced against air fares and hire of vehicle plus only having very minimal gear with.Say about $900 return airfares - Adelaide and about $200 per day hire of 4WD.

To me the best deal would be to put the Landcruiser on the train and fly up. This would depend on how much the fee is increased for an unaccompanied vehicle. ie $1676 return + $? That way you would have an equipped vehicle, save the vehicle hire costs say the long train journey or longer drive. If staying for about ten days or longer (and hire vehicle for this long) it would be cheaper.