The fact is costs so much means, firstly, we might as well get it over and done with and secondly, you are creating history, which is priceless. Nevertheless, actually, it can give us a profit, depending on the model. I support the State Governors simply rotating, annually, as President (as the GG costs us 13 m each year, so that disappears - the State Governor gets no extra pay);* and don't forget everytime a monarch dies that means our coins have to be changed and of course, it can be very cheap: just phase everything out over 15 years (in other words, it costs nothing as we change things every few years anyways). You also seem to forget federalism atm is costing us 49 m per year on paperwork and the occasion gift to Liz; frankly, its your system that is costing us.
Oh and Chief Justice French recently did an article for the Sydney Law Review, discussing ways a dictatorship can be installed under the status quo (so just because it "ain't broken" doesn't mean it can't be broken) - oh, and there is a reason to change: we have a philistine as our Head of State,** someone who stems from William the Conquerer, killing, stabbing, murdering the native Britions and installing himself King, ha:
http://www.guardian.co.uk/uk/2007/dec/22/monarchy.topstories3
Nevertheless, I support slow, statutory reform: start by simply applying the model to the GG atm (so the PM advises the Queen to rotate the GG among the State Governors annually, a list of 8 people is nominated by a 3/4 majority of State Parliament, people choose). The model ought to be in practice, trialled and tested. Then simply crystallise the statue into the Constitution, come the referendum.
As such, your views are dismissed.
* This model is the most stable model in human history, Switzerland has a similar system, producing 300 years of stability.
** Judicial decisions of the High Court which declare the Queen, not the GG, as our Head of State: Pochi v Minister for Immigration & Ethnic Affairs [1982] HCA 60 at 9, Re Burgundy Royale Investments Pty Limited v Westpac Banking Corporation; the Northern Territory of Australia [1987] FCA 454 at 8, Nolan v Minister for Immigration & Ethnic Affairs [1988] HCA 45; (1988) 165 CLR 178 at 10-11, The Queen v Sam Scott (1993) 114 ACTR 20 at 66-70, Authorities Superannuation Board v Commissioner of State Taxation (WA) [1996] HCA 32; (1996) 189 CLR 253; (1996) 140 ALR 129, Moller v Board of Examiners [1999] VSC 55 at 19-25, Sue v Hill [1999] HCA 30; 199 CLR 462; 163 ALR 648 at 83-88, Kingsman v Health Administration Corporation [2000] NSWSC 136 at 258-9, Buchanan, Donald v Lindisfarne R & SLA.-Branch and Citizens Club Inc and Returned and Services League of Australia [2003] TASADT at 13, 69, 79, 81, 85, 87, 94, 115, Services League of Australia Limited (Costs) [2004] TASADT 2 at 14-19, 21-24.