Hi Jean, I think your offer is reasonable in $A terms as they are scarce and the nearest you can get to the KN7 is Korg at about $4000 (plus the speaker, approx $600 so I am told) or Tyros 4 at ?????? S/H on e-bay was asking mid $5000.
All that Bill said is correct. You can get the 2GB cards if you google them and you do not need anything larger for the KN7. I would suggest that you buy a few when you find them, I feel they may be discontinued in the near future.
Good luck with your purchase, you will not regret it.
Ray