An estimate of enhancement cost for the F-111 to maintain a good capability out to about 2030 was around $2.5billion whereas the Super Hornets will cost something like $6.5billion.
Bushranger: a comment on the ability to keep old airframes alive.
A variety of program and budget and cost decisions time and again run into, ten years later, parts, vendors, and sub contractors either jacking prices for parts up, or simply not making the parts any longer. This kind of "death of a thousand small cuts" creates downstream cost burden legacy (see F-111) platforms since industry time and again finds it uneconomical to support small numbers of these old airframes.
I have recent personal understanding of non-trivial problems in supporting non-glass cockpit, and legacy avionics in the US Navy's T-44 trainer. This is a few years ago, mind you, but what it amounted to was a cheap, legacy program becoming significantly more expensive to support and sustain due to parts obsolescence ... sure, industry would get us repair parts, and significant mark ups. Fatigue life is a separate (but non-trivial) related issue.
With that in mind, you then run into "pay me now" with a bit more, or "pay me later" when you have no choice but to upgrade -- at the systems (sorry, $ystem$) level.
On that basis, and on the criterion of fewer maintenance man hours per flight hour, the Super Hornet may not have been the weak decision you suggest it is. (My being a Yank in no way biases this, as both are originally Yank platforms ... 
)
Super Hornet requires K-30 to achieve things the F-111 could do without tankering so that does not equate to cost-effective operations in my view.
I suggest that your modern archipelego operations would benefit from the F-18's availability.
I may misunderstand your mission requirements for the fighter arm, but if you need to loiter, it's good practice to launch, tank, then proceed on to your mission. That was a common practice for our Navy, and became increasingly common in the more recent fights due to the need to loiter and await calls for fire ...
As a last point, which is related to one of my first contributions, the political flexibliity that the government accrues from an additional C-17 for "non mil" operations (see the Japan example) seems to me one of the reasons that the pol folks allocate the money to a platform that is "dual use" rather than "tactical military use" in terms of its capability.
I'll paraphrase a discussion Colonel Harry Summers had with a NVA counterpart some years after the Viet Nam War
"It doesn't matter how good you were tactically if, at the strategic level, your country was aiming at the wrong target with the wrong weapon."
To put that into the context of the discussion here, with regard to how to spend short dollars to meet Australia's overall strategic needs, I'll open with the Axiom that a nation's military tools and capability are acquired to serve its strategic interests, (the use of armed forces to achieve politically defined ends) which requires competence at the tactical level, and a suitable tool kit.
That said, the strategic interests aren't always combat critical, but the uniformed folks happen to be
a) damned good at what they do
b) dependable,
c) organized, and
d) available without negotiation or yet another contract needing to be ironed out.
Your C-17 is thus a tool that gives the Australians a strategic capability that serves her strategic political interests. (We in the US consider C-17 Strategic/intertheater lift and C-130 tactical/intratheater lift). The risk decision made regarding what the uniformed folks will make do wit at the tactical level for most plausible scenarios is the same old thing ... where "worse case scenarios" are to be found, that was a risk decision taken. (Having spent a few decades on the uniformed end, I appreciate your frustration with how the pols time and again do that to us 
.)
The next question is: at what level does Australia deal in strategic infrastructure development in their near abroad? Non-military, government funded aid that helps upgrade or create higher quality air strips ... that allow larger planes to phase in Australian forces on an as needed basis when the speed of air transport is a tactical requirement ... that's not mil equipment money, but it's money spent for the local theater of operations that would aid and abet your mission accomplishment.
Does Australia do this or not?
That isn't a weapons procurement question. It is a theater level strategic question (both pol and mil) that uses "dual use" money to position a military capability that your services will need in the case of rapid reaction force deployments.
Last edited by Lonewolf_50; 11th Apr 2011 at 16:48.