Good info Nino. The customs duty for pinballs is in fact 5 per cent (Chapter 95, Schedule 3) but as you note (amazingly) there is a tariff concession that negates it.
9504.30 PINBALL MACHINES - Coin Operated
Op. 22.02.1988 Dec. 25.05.1989 - TC 8802725
Still have to pay gst of course - but the 5% would have a discernible impact - especially as you would pay the 5% duty & then gst on the value INCLUDING that duty. The industry must have had a bloody good lobby group at some stage.