Cheers and thanks for the tip, Cavey! Had a poke around and saw
this was advertised on Aussie Arcade a week ago. Still seems a little pricey even without going by your prices (though obviously that helps), but I think I have a firm idea of what price I would personally pay: ~$2200 in reasonable nick with a little bit of work needed (but big stuff like PF and majority of plastics perfect) or pushing $2500 with everything near perfect including new cab decals.
That one on Gumtree ended up being sold as soon as I contacted the guy anyway, but at this stage it looks like a game that crops up fairly often considering it's low production run. If I miss out on one, I'm sure another is right around the corner! I still haven't played a real machine yet, but driving from Geelong to Moorabbin tomorrow to play a sited one, at least have to make sure it's a machine I'd like!