GK - The "sunk cost" argument sounds powerful, but is not actually a guide to future behavior. As an investment-oriented friend reminds me, "every smart portfolio manager occasionally accepts ugly losses on disappointing investments in order to redeploy funds to better opportunities."
The big JSF money is still ahead - basically, the current plan eats most USAF and Navy/Marine aircraft procurement money between now and 2030, excepting the tanker and T-X. So, no new bomber, and even if all goes well (which it has not done so far) more than half the USAF fighter force in 2030 comprises jets ordered 40+ years before.
That's why most independent budget studies, other than those that isolate the Pentagon from fiscal reality (and have been dead letters since the election), call for changes to the JSF program. SecDef nominee Hagel has endorsed the Simpson-Bowles plan that cut back F-35A/C and whacked the B.
And "nearly complete" is an odd description for "seven years away from IOC with the original planned capabilities."