I agree with Tac that in the normal course of events the offers you have received may seem and probably are derisory. However, I go back to a point I made in my initial post - you have the right loco in probably the wrong location. I doubt there is a large enough easily accessible market in Aus' to generate the prices you might be hoping for. It may take a little time to market that loco and find a buyer willing to offer near the amount you envisioned where you are.
It's "home" market, where the greatest interest will be to create that market to drive the price, is probably north America. Even there interest may be limited and as a result the maximum value will be affected when you have to offset the known risks and costs of shipping from your location as well. Any potential buyer will be aware of these factors that need to be accounted for, especially if it is a trader willing to take a punt but still in need of turning a profit. Even in their original, as factory shipped, packaging Accucraft's larger loco products were really intended to be moved as "groups" of items, Hence Tac's experiences with his Royal Hudson. Look at Bachmann locos of a similar size for comparison, though they are a lot lighter, because of the larger production runs it was economical to have form fitting styrofoam packaging to protect them, as new or used, and a shock proofed outer boxes too - they are seen as a much lower risk to ship as a result.
You might be better off posting in one of the US based garden railway or Gauge 1 forums to get a better idea of interest and views. And be very clear of its condition and unsteamed status. That can be very important to buyers, particularly those who want it as a display item with "investment" potential. Sorry I cannot be more positive. Max
P.S. The transport cost is always a loss.