The Super Hornet program is a reverse example of the F-22 and probable costs of the F-35. With those two programs, as planned purchases have been cut, per aircraft costs have soared.
With the Super Hornet program, the addition of a dozen 4 plane squadrons drove down the per unit cost to the point where Super Hornets are now costing about $50-55 million a piece. Then the Aussies got some, then the Navy added some more.
F-35 per unit costs will continue to climb as more aircraft get cut from the buy.
We bought 24 Super Hornets to replace the F-111. The sensible thing is that half of the Super Hornets are wired to become Growlers which gives the RAAF a huge capability boost.
In return we share some EW technology with the US that we’ve been working on.
Unit flyaway costs didn't change appreciably with an Aussie order of 24 aircraft. The Navy put a lot of money into developing the Super Hornet after the A-12 disaster, and if those developments costs are included, then yes, total cost per aircraft goes down with each additional purchase.
Same would be true if we bought more F-22s. Unit flyaway cost of the last couple of aircraft is about $150 million, but total program cost including development spread over 187 aircraft is about $380 million. That total cost would also go down with each additional aircraft purchased.