my blunt opinion is if you don't own the .com.au then don't own the .net.au
if you own the .net.au only then there is only one potential purchaser ! the .com.au owner and they will take the HIGH ground on you so the price will be low, if at all
nice .net.au like I think these are could fetch some money because the .com.au owner may want to protect themselves so maybe you would get to $500?
others will say NIL and potentially that could be the case, once again its the cost of time to get the sale so you end up working for $5 an hour.
tim