I just spent half an hour looking at every auDA Accredited Registrar's website, looking at how much it costs to register a .com.au domain.
Sometimes they actually listed prices, but often the easiest way was to just search for a random domain and wait for them to tell me what it would cost. It's just a quick survey, and it's quite possible that I got some of them wrong. All the prices should be for 2 years, but I didn't read the fine print too carefully. I expect some of the URLs won't work without the POST data, but they're really only there as hints for the auDA list.
http://www.aussiehq.com.au/business/domains/
$59
https://manage.planetdomain.com/order/execute/multiDomainSearch?domainName=asdgasdfasdf&tlds=.com&tlds=.net&tlds=.org&tlds=.mobi&tlds=.asia&tlds=.biz&tlds=.info&tlds=.com.au&tlds=.net.au&tlds=.co.uk&tlds=.org.uk&tlds=.us.com&tlds=.us&tlds=.ca
$33
http://www.clickngo.com.au/domains-pricing.html
$59
http://www.webaccess.com.au/domain_names/home.html
$49.50
http://www.ddns.com.au/prices.php
$65
http://intaserve.com/
$27.95
http://www.domaincandy.com.au/pricing.asp
$99
http://www.domainregistration.com.au/
$127
http://theconsole.netregistry.com.au/order/execute/domainSearch
$26.97
http://www.mdwebhosting.com.au/myaccount/domainchecker.php
$18
https://secure.westnethosting.com.au/signup/stage2.aspx
$88
http://www.austdomains.com.au/pricing.html
$69
http://www.domaincentral.com.au/
$37.95
http://www.namescout.com/dot_au.asp
$27.45
http://www.melbourneit.com.au/cc/order/vieworder?&action=addtobasket&d-asdasdfasdf.net.au=asdasdfasdf.net.au&recheck=true&d-asdasdfasdf.com.au=asdasdfasdf.com.au&added_catalog=1895165,1895166,1895167,1895168
$140
http://www.domainbandit.com.au/site/domain_search.cfm
$66
http://www.tppinternet.com.au/domains/search-results.php
$99
http://www.safenames.net/DomainNames/DomainRegistration.aspx
?
https://ssl.smartyhost.com.au/signup
$40
http://www.cheaperdomains.com.au/hspc/index.php
$35
http://www.bottledomains.com.au/
$99
https://www.enetica.com.au/register.cgi?action=lookup&ludomain=asdfasdf&x=79&y=11&domaintype=.com.au&domaintype=.com&domaintype=.net.au
$69
http://www.domain8.com.au/
auction
https://www.instra.com/en/domain-application/login/step-01
login before price
https://www.anchor.com.au/domain-name-registration/domain_order.py
$69
http://www.explorer.net.au/show.php?f=pricing
$99
http://www.godomains.com.au/welcome/
$98
http://www.connectwest.net.au/termsconditions/tc.cgi?domainName=asdgasdgasdfg&tld=com.au
TOC before price