The bits that are different would actually be cheaper on the hunter. The 32 mark 41 vls would probably be cheaper then the RN's 24+8 option. The 8 anti surface and land missile launchers are the same as what the Adelaides and Anzacs have and can probably be transferred to these new ships. The adelaides had 8 mk41 and these can be pulled out and used on the new ships. The torpedo launches from those 6 ships could also be transferred to the new hunters.

The electronics while different should have a similar cost especially as they are likely just newer versions of what is being used on their current fleets as the ceafar 2 is of the ceafar on the anzacs. There is not the significant difference that you make out to be in either platform.

Anyway the point is that things cost more here in Australia and there are so many other things like roads, other PT, schools, hospitals, emergency services, water and other things that take up the share of the pie and state Governments aren't interested in funding something that the Federal Government is supposed to be supporting. Things cost more here and that is the way it is.