Just be aware that there's a lot more to that question than cost. Whilst RA-Aus have done some brilliant marketing over the years there is a lot more to the decision than simply dollars. The maintenance standards of RA-Aus aircraft are probably the most relaxed area. Word is that a flying school recently had its entire fleet of RA-Aus aircraft grounded on inspection by CASA for being unairworthy. They'd been merrily training students in one aircraft with an engine 1,000 hours overdue i'm told. Whilst this could happen in GA it's almost impossible with the checks and strict liability provisions on LAME's.
That's just an example of one possible difference. There are a lot of good, honest RA-Aus schools and hire aircraft but the maintenance and training standards between them all is unbelievable once you start looking into things. There's a lot of variation in the GA schools and hire aircraft also of course.
It starts at the philosophical level really for me. A GA aircraft was designed to a standard of "how strong does this need to be" whilst modern RA-Aus aircraft are designed to a weight "how heavy can this part be". That's the first starting point when comparing a Jabiru/Tecnam to a 150 for me.