I thought the RAAF bought them used?
No, they were ordered by Australia as the F-111C variant, which went into service in 1973 (they actually received them in 1968, but there were technical problems which delayed their acceptance into service).
http://en.wikipedia.org/wiki/General_Dynamics_F-111C
The RAAF bought F-111Cs brand new off the General Dynamics showroom floor in 1963. Development problems and minor issues such as the wings falling off of USAF F-111As delayed delivery until 1973, flying F-4s as interim aircraft.
After the USAF retired the FB-111A/F-111G (SAC strategic bombers later given to TAC and redesignated F-111G,) the RAAF bought some of those as used.
But the F-111C was and is exclusive to the RAAF.
24 Bought new as F-111C in 60s. Upgrade (Digital avonics Pacer Strike equivilent) late 90s
4 exUSAF F-111A purchased as attrition replacements late 70s
15 exUSAF F-111G (exFB-111A) purchased early 90s for training missions