Hello and welcome to the forum.

Brick-and-mortar coin auctions are always tricky things to predict. Coins might go well above estimate, they might go well below. "Flagship" coins like NSW Dollars and Dumps often go for above estimate; the auction houses like to put such estimates on the low side, because high-profile coins that get written up in CAB Magazine as "sold for above estimate" makes for good publicity. However,
this coin was passed in at Noble's recent auction at $17,500 estimate.
But identifiable Dumps can be obtainable for less than $9000 - considerably less than that, if you're prepared to overlook some problems that might be deemed unacceptable on a commoner coin. At the previous Nobles auction in April, there were
five dumps sold. The two nice, problem-free examples sold outside your price range, but two were estimated at $3000 each, the worn one sold for $3000 and the damaged one for $2200, while the fifth was so badly scratched and worn they didn't bother taking a picture, it had an estimate of $200 yet sold for $800.
Don't forget to add 16.5% "juice" (buyer's premium) to the final knockdown price.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis