(N.B. This is a blog post I wrote on Google+ in 2014, which had since disappeared from the Web.)
The NIST study concluded that "the impact of inadequate software testing infrastructure on the US economy was between 22.2 and 59.5 billion dollars".
As usual, people mention this figure as if it was an undisputed fact (for instance, you can find it on a couple Wikipedia pages). It's a good bet that they haven't read the original document carefully and critically. If they had, they might have noticed some red flags in the "study" and would at the very least hedge by emphasizing that it is an estimate.
There are two important aspects to any estimate: precision and accuracy.