The Perth auctions have always been way overpriced in my opinion making them no different to any other auction anywhere else.
One of the first pins I ever got was a 6Million $ Man at $1600 with worn playfield, faded cabinet and 6 burnt displays and didn't realise until later that the fat cnut bidding against me was the owner doing a shill bid. I realised this when I saw him bidding on heaps of other machines and not actually winning any bids. At least i was only ripped off about $600. If it was a top end pin it could have been thousands. I Guess the experience of this cost me $600 but I am much wiser now so it wasn't a total loss.
Like others have said, you have to do your homework before you go to an auction so you can know what a fair price is for a particular machine depending on its condition. I mean you wouldn't go to a car auction without first checking the average going rate for a particular car in say, the Trading post or Quokka.
I do feel sorry for anyone ripped off but its their own stupid bloody fault for not doing their homework first. Maybe next they will be a bit wiser for the experience just like I was.