#1 What all do you get for $500
#2 Who are the instructors?
#3 Are they lecturing??
~trunk show???
~buy all my cool products?
~or are you sewing?
#4 As you said it is hard to compare US -vs- Aussie prices. but my professional workshops in the US cost $300 for 2 days.
#5 I think you can buy a lot of fabric for that much money.
Good luck deciding.