If you consider the material cost + the hours, these prices doesn’t seem too crazy to me (mostly considering AU humanhours are probably not cheap).
The shredder material costed around 2000€ when we designed the V4 version in 2019, since most of these material almost doubled, so probably around 5000 to 6500 AU$ for the material alone currently, to that you can add 1 to 2 weeks of work. If the machine shop is not able to build these machine is little series, it would be hard to optimise its prices.