Have atended a couple of auctions of stock from closed motorccle shops previoulsy, Redwing Honda in Heidlelberg and Jeffery (I think it was) Honda in Fern Tree Gully here in Melbourne.
Both times attendance was full of aggressive wannbee, red-neck, know alls. Bids on many items was a frenzy with some items going for well over value and sometimes RRP. There was even some push and shove, nearing punches, requiring security to remove some attendees from the building - but this wouldn't happen in SA.
If there is something specific you have in mind / need, and you have done your homework re. value, you may be able to pick-up something at a good price, otherwise the small savings are not worth the hassel.
Just my humble opinion.