Use the discount code for $6 off. Membership fees vary, e.g. $115 / year for a typical full year. Memberships are pro rata, so it seems that today's price is $64.41, minus $6 brings it down to $58.41. All memberships expire on 1 July, so after that date it'll cost $115 to renew.
Membership page: https://bicyclensw.org.au/membership/
Note: I'm not a member, I haven't decided if it's worth it for myself. The main benefit seems to be accident and liability insurance, doesn't cover your actual bike.
Does it give you rights to ride on the road?