AU$1m = AU$1,000 x 1,000
AU$1b = AU$1,000,000 x 1,000
AU$1t = AU$1,000,000,000 x 1,000
Technically a millionaire is someone with net assets of $1m (total assets less debts, inc PPOR) but this is an easy milestone for many these days.
I agree a true millionaire is someone who can stump up...