No, you haven't been ripped off. I bought the same thing for $20 from my local BigW (although I knew exactly what it came with). I can't think of any shops in Aust. that sell JJ2 now - haven't seen the full retail on shelves since it came out (late 1998) to late February 1999. You can try and get the shops to order it in, order from overseas (check J2O newsposts - there's a link to an online shop that has/had 7 copies of JJ2 left), get it 2nd hand from game shop etc.

you could also try contacting Aiko and see if he has any copies of JJ2 left (doubtful, however).