I can't remember off the top of my head how much you can convert from RAAus to PPL hours
All of it if it was in the type of RA-Aus aircraft that could be VH registered as well.
So assuming you have done qualifying navs, all you technically need is the PPL theory exam, 2 hours of instruments, recommendation flight and check ride. If you go to a school that has your ultralight in a VH-registered version, even easier. Probably worth traveling for. (you can do all the training in an RA-Aus aircraft as well, just need the check ride to be in VH.)
Unfortunately, few GA schools seem to know this and instead of making it purely competency based, they generally make people jump through the hoops of getting an SPL first and then do the entire syllabus of navs. So a lot of people are looking at spending a lot more money than they need to.
(And then of course, there are people who simply need at least 10 hours just to just learn to fly a Cessna or Piper, just as there are GA pilots who need that many hours to get to solo a Jabiru. Both should probably find another hobby...)