Personally I don't like domain hacks, mainly because they bleed traffic to .com and in this case probably .com.au too.
Many consumers mistype domain hacks, and they often add in '.com' or '.com.au' because they're unaware that '.ly' is the extension. This makes branding a nightmare, you have to do things like emphasise the dot so that people are more likely to realise that it is '.ly' not '.com' or '.com.au'.
Successful businesses that have built their brand on domain hacks will often chase the .com once they have the funds to buy.
For the reasons above my valuation is: reg fee - $100.