Here is a good example, airfares are cheap and unregistered you would get it heaps cheaper.
http://www.bikesales.com.au/bike/search ... ex=33&x=13
All you have to do here in Qld is the owner removes the plates and deregisters the bike.
You as the rider/buyer get a receipt for stamp duty in NSW and an unregistered vehicles permit from Qld Transport for set number of days and ride it home and register it in NSW.
However all though not compulsory and non transferrable in other states its good to have the owner get a roadworthy on it anyway, here in QLD it is $30 bucks I think.
Thats of course if you were looking to buy interstate.
If I ever get another bike I won't rule out going interstate for the right bike.
Nothing At All.