As I understand it, if I were to obtain a Recreational Pilots Licence and wanted to add the navigation and passenger carrying endorsements, the time and money investment is then similar to the standard PPL?
Blue Bandit, your statement above leads me to believe that you may be confused between a Recreational Pilots Licence (CASA) and a Recreational Pilot Certificate (RAAus).
If you gain a RPL(CASA) then there is no requirement for extra training and a passenger carrying endorsement does not exist. It is part of the Licence.
If you gain a RPC(RAAus) then you do require extra training prior to being granted a passenger carrying endorsement.
If we return to your original question regarding flying a C172 or Warrior, you can fly those with a RPL(CASA) but you will not be able to fly them with a RPC(RAAus).
I hope that clarifies the situation. I apologise if I have misinterpreted your original intent of the question. However after working with both regulations and training in both CASA and RAAus environments, I know since Part 61 and the change from GFPT to RPL(CASA) alot of people simple confuse the Licence with the Certificate and visa versa.
Stretch