If they'd bought a new carrier then, maybe we'd still have one now (a proper carrier, that is). 
The US were very keep to supply us with an Essex in at least CVS configuration and the Brits offered us Hermes in 68, with Victorious and Eagle also being available following the decision to get out of the carrier game. The ships were on offer for next to bugger all, I believe possibly for less than it cost to refit Melbourne to operate Skyhawks and Trackers and improve her air-conditioning. They required more crew than Melbourne but less than Melbourne and Sydney (as a troop transport) combined.
Not quite. An ESSEX class or an EAGLE required approximately 3,000 men. A MELBOURNE 1,350 men. You could have had one ESSEX or EAGLE for two smaller carriers as far as manpower requirements, approximately. An ESSEX or an EAGLE would have been more expensive to run than MELBOURNE or SYDNEY. SYDNEY in particular had essentially a skeleton crew, without air Ops or air complement. I am unsure of costs. EAGLE would have been cheaper to purchase than an ESSEX I suspect but more expensive to maintain.
The argument about money is flawed as Australia has consistently gone for the cheaper option while wearing rose tinted glasses, causing delays, capability gaps, followed by costly mitigation. The number of times a fully costed, risk assessed and engineered option has been knocked back in favour of something that promises the world but never delivers the promised capability is quite shocking. Even the F-111 buy was a cost cutting exercise, buy 24 (plus 6 recce) high end airframes for two squadrons instead of 36+ perfectly good enough airframes in three squadrons, supported by tankers. I could be wrong but I believe the F-111 ended up costing more than the Phantom fall back option would have.
Hindsight is wonderful. The RAAF wanted an up-to-date replacement for the Canberra and the F-111 was the only game in town that fulfilled that, in their opinion. The Buccaneer was too naval, the Mirage IV was not yet available. The problem was the F-111 was reaching too far with it's variable geometry wing. Treasury wanted value for money. The F-111 appear to offer that. Both the RAAF and Treasury were betrayed by the technology.
Imagine 150 Phantoms replacing Canberra, Sea Venom, supplementing, then replacing Mirage. Not cheap but what would the savings have been on the support systems side of things? Phantom was much more capable than Mirage or Skyhawk, and good enough that the RAAF wanted to keep the leased Es, even after the F-111 arrived. Phantom would have needed tankers to match the F-111s range but we ended up converting 707s anyway, so the KC-135 would not have been a significant extra cost anyway. Had we gone for Spey Phantoms, or B/J/N/S the 707 with hose and drogue would have been perfectly adequate anyway.
Problem was numbers of 707s. There simply weren't that many. The RAAF ended up with the last discards form QANTAS. The RAAF ended up with three airframes, hardly enough to sustain even a flight on a long distance mission. What we needed were about a dozen or more airframes. That would have meant purchasing them, something the Treasury wasn't interested in doing.
I'm not pulling this stuff out of a random orifice, it was proposed and rejected, with the options selected instead delivering less capability, while still costing a significant amount up front, then even more down the track as the reality of sustainability, obsolescence and capability short falls hit. Modernised Melbourne was barely capable of operating Skyhawks and required the cannibalisation of retired carriers (Bonaventure and Essexs) to keep her operational, a Squadron of Mirages had to be disbanded to sustain the shrinking fleet and even then there was a period of years in the late 70s early 80s where neither their guns or air to air missiles were operable. Then there were the F-111s teething issues that took years to sort out. None of these would have occurred had the Phantom been acquired and Melbourne replaced in the 60s.
No one is suggesting that you're pulling it out of your bum, mate. Yes, it was proposed but the rejection occurred on what were considered by Treasure to be good reasons. Look, Treasury were a bunch of bastards and are still a bunch of bastards. They didn't believe the Leopards were a good purchase and kept trying to retire them early, so much so that Army lied in Senate estimate committee hearings to downplay how much it cost to keep and maintain them. What the RAAF and the RAN needed was a good enough reason to get it past Treasury and they failed on that, each and every time the proposed something. It would have been much easier to shoot all the Treasury officials and have a coup. 
Sorry to detract off topic, but after years of contemplation and maturity, my blinding effectionet for the F-111, I've settled comfortably on the notion that Australia/RAAF should have gone with its original findings and selection of a 'Canberra Replacement' - the North American A-5B/RA-5B Vigilante! In terms of cost, the number of platforms (36 vs 24) and it's real and practical 'in-service operational date of 1966'.
On top of this, with the money saved with a Vigilante purchase, the same fact finding tour actually looked at the Boeing KC-135 Stratotanker....
As in my
Alternative ADF ORBAT, the RAAF gets its Vigilante's and KC-135's...in 1974 F-111E's are purchased to replace Vigilante, while the KC-135 continue a long and productive career continue supporting the RAAF in its entirety - AWACS, transport and Maritime Patrol, etc and not just the F-111's - watering down geo-political issues with you know who!
MAD