F-35: So are lifetime cost estimates so much garbage?

That's sort of the impression I got reading this article about what Frank Kendall said concerning them:

In late August, Bloomberg News reported that Lt. Gen. Christopher Bogdan, the head of the F-35 program, estimated that O&S costs have dropped to $857 billion. Previous government estimates have put the lifetime O&S costs at $1.1 trillion, a number proponents of the fifth-generation fighter have said suffers from unfair projections of inflation over a 50-year period.

When asked about that report, Kendall indicated that estimate may be overly optimistic.

“I do expect it to come down. I don’t know if it will come down as much as [Bogdan’s] number, but we’ll take a look at it,” Kendall said. “He has a basis for it. The problem with that number is there are so many different assumptions you can make and too many different ways to calculate it. I don’t want to be overly optimistic and I don’t want to be overly conservative.”

“So, we’ll take a look at the assumptions he made and we’ll look at what CAPE comes up with and see what we want to use as an official estimate.”

"... so many different assumptions you can make and too many different ways to calculate it."

Then what is such a number worth if it is open to that many different assumptions and way's to calculate it?

Legitimate question.  As Kendall points out, at least Bogdan's number uses actual data (his "basis for it").  The rest?

Pretty much assumptions that may or may not be worth much.

Graff