To guage a very ballpark figure if you are considering building, there is the following link, just as a starter.
http://homebuilding.cordell.com.au/index.php?c=survey&profile=21&summarys=1
It's through Allianz Insurance, essentially for replacement rebuilds I presume.
The good point is that all the figures at the Back end come from Cordell Estimators, who along with Rawlinsons, are the main Costing Source to the Building Industry.
The link goes through a "quick calc" scenario, but when completed, there is an option to do a more detailed spec, as it asks for more info.
Unfortunately, it appears you need to complete the quick cost first.
I copied the link to the second stage costing, but that required a login and password. Sorry, no shortcuts. just zip through part 1
I've seen similar on other Insurance sites, but forget where.
The costs would all be as if a builder was doing the whole job, but could be handy for OBs when declaring the value at Planning Permit stage, and, naturally, when shopping for Insurance after your work is done.
Recommend Greenify's sheets when you are getting down to real details. Plus you can then work out your savings by going OB.
No affiliation with either.