RAND states the increasingly obvious: "Joint" fighter programs are a waste of money.

http://www.defense-aerospace.com/article-view/release/150301/joint-fighter-programs-cost-more%2C-add-risk%3A-rand.html

Main conclusions being:

1. Joint Aircraft Programs Have Not Historically Saved Overall Life Cycle Cost
•Historical joint aircraft programs on average experienced substantially higher cost growth in acquisition (research, development, test, evaluation, and procurement) than single-service programs. The maximum percentage theoretical savings in joint aircraft acquisition and operations and support compared with equivalent single-service programs are too small to offset this additional average cost growth that joint aircraft programs experience in the acquisition phase.

2. Joint Strike Fighter Is Not on the Path to Achieving the Savings Anticipated at Milestone B
•Under none of the plausible conditions analyzed did Joint Strike Fighter have a lower Life Cycle Cost estimate than three notional equivalent single-service programs.

3. The Difficulty of Reconciling Diverse Service Requirements in a Common Design Is a Major Factor in Joint Cost Outcomes
•Diverse service requirements and operating environments work against the potential for joint cost savings, which depends on maximum commonality, and are a major contributor to the joint acquisition cost-growth premium identified in this cost analysis.

4. Joint Aircraft Programs Have Historically Been Associated with a Shrinking Combat Aircraft Industrial Base
•The presence of fewer prime contractors in the market reduces the potential for future competition, may discourage innovation, and makes costs more difficult to control.

5. Joint Aircraft Programs Could Increase Operational and Strategic Risk to Warfighters
•Having a variety of fighter platform types across service inventories provides a hedge against design flaws and maintenance and safety issues, which could potentially cause fleetwide stand-downs.
•It also increases the options available to meet unanticipated enemy capabilities.

Full Report (pdf)

It would have been more interesting if they had compared their projected “Joint” budgets with the F-22, EF2000 and Rafale budgets to get a better idea of how accurate their projections were. The F-22 went overbudget as well, albeit not to the same grotesque amounts as JSF.