I realise that there is different registration costs - I even went to the Vic Roads sites (as linked from your spreadsheet). Because it's dependent on registered postcode, I can't give exact registration costs, and neither can your spreadsheet (since it just accepts 'Vic', not postcode (and the entire calculation behind that postcode aspect)).

Admittedly the difference is minimal, but someone in postcode 3000 is going to be paying $98 more for rego than someone in postcode 3100, for the EXACT same car, purely on rego costs. So, this also introduces a margin for error into your spreadsheet.

I appreciate the work you've put into it, and it was very helpful to me when I was looking for a price on my Golf R (and it's part of the reason I've contributed to this site - I figured the donation was more than offset by the saving I made as a result). However, it is only an approximation - some states have simple systems that can be matched easily, others like Vic that are postcode dependent can only be approximated without adding huge complexity (such as backend queries into the Vic systems to get exact rego based on postcode).

The lowest Vic rego for new cars that I found was $526. So again, taking a conservative estimate approach, using $500 is going to point to a minimum amount available to play with, and in all likelihood it will be better. Sure, there's a margin for error, but it will be in Danny's favour.

An alternate method Danny could use is to put in all his figures into your spreadsheet, including the dealer discount required to get to $57k on road. Then either add in the ACC and DynAudio options to see if the LCT value becomes non-zero, and if it does, work out what additional discount is required to get back below. I reckon it will be less than $250 (based on my calculations above) if it requires any discount at all.