Sometimes, things don't cost what the original MSRP price tag shows, especially if improvements are needed for what is revolutionary or a leap forward from previous technology. Now, I don't know at what point or what dollar amount becomes the limit; that's outside my scope.
But I just look at history and look at another aircraft that had a very rocky development start. One that was another joint service program, at least initially. One that was revolutionary in design and capability; and in which required some serious upgrades after previously unknown problems/issues were discovered and had to be fixed with the jet, costing some hefty cost overruns.
That plane was the F-111. From it's revolutionary concepts such as variable geometry (swing) wings, to the first afterburning turbofan engines, to terrain following radar and the automated flight control system tied in with that; the jet had a very steep learning curve that came with it. It's initial combat deployment in 1968 in Vietnam was a disaster, with 3 planes lost out of 6 deployed due not to enemy action, but to previously unknown design issues. However once those issues were fixed (costing more money) and the plane returned to Vietnam in 1972, it became one of the most feared aircraft by the North Vietnamese, next to the B-52. It became one of our only USAF aircraft able to go against the Cambodians during the 1975 Mayaguez incident. It was the primary strike aircraft of the 1986 Libya raid, flying the longest tactical-jet strike mission ever, and it became the most successful and versatile aircraft of the Desert Storm air war. The F-111 went from being a joke, to becoming our most successful all weather, low level, day/night strike interdiction aircraft, along with the A-6 Intruder. As well as having an Electronics Countermeasures version built just like the EA-6 Prowler; as well as a strategic version for SAC for long range nuclear strike. In the end, we got our money's worth out of the F-111, and it would've survived for longer had it not been a victim of the 1990s budget crunch.
The F-35 may not be perfect, but some of its true capabilities are just now becoming realized as newer software and design upgrades are incorporated. Where and how the fiscal end comes in money-wise and to what end that should be reigned in (or can be), again is beyond my scope in terms of actual $$ numbers. But capabilities-wise, the F-35 is indeed coming into its own with its revolutionary design and previously unheard-of changes to our own Tactics, Techniques and Procedures that the technology it brings, is causing. Some of the old ways of "doing business" on the battlefield, are indeed going the way of history.
