There was one that sold for around $500 on TM but it was not that good, d & t & missing the rear sight iirc, the No8s i have seen sell at auction over the last couple of years have sold between $550 & $800ish but on the day anything could happen, could be as cheap as $350 or over $900.
I have the details of the Cadet auction as i went, paid less than $800 otd for both my No8s & just to add insult to those out there who have to pay a lot more for a No8, the NZ$ was worth US$0.50 on the day, the lowest i have ever known.