Changes hands regularly. For a game that has a production run of 350, it is easy to find. Considering Hankin was an Aussie company, not that many were exported. It would be VERY rare overseas and for that reason, sought after.
In today's "buyer's market", you should get one for $1000 - $1200.
As a player, its a real plodder, and shares a similar playfield layout to Bally Space Invaders.