well its a niche domain and this type of tourism is gaining ground, the downside is the hyphen and the .net.au , although if you are a site and supplying good information i am sure it would do ok , in germany as we all know hyphens are actually more common so that's no drama and if developed the ,net.au can still fly for that term although better to sell as a pair i guess
my guesstimate is high xxx to low x,xxx depending which is getting sold , or $ mid x.xxx for both