I don't know about Australia, but here in midwest USA pawn shops often have good deals on low- tomid-range bikes with prices of less than 50% of brand new. For example, I picked up a rigid MTB of about US$400 new for $100--and it had obviously never been ridden at all! More expensive bikes are hard to find. When people spend > $1000 for a bike, they usually know exactly what they want and intend to hang onto it, I presume.