Payment is based on COST incurred, not delivery. Or expenditure to a limit regardless of outcome.
For Webb we have this:
"All told, NASA has spent about $9.7 billion on the project, which has been delayed by more than six years in the past decade. That's in stark contrast to estimates for the project when it was approved, when it was meant to cost $1 billion to $3.5 billion and launch sometime between 2007 and 2011, according to the GAO report."
Can I ask who is footing the bill if this was payment as delivery was met? Oh right, because it's not.
The only recent efforts towards fee for service were the HLS award and some of the commercial crew program work. Interestingly, the women heading that up (Kathy - very successful) appears to have been sidelined from directing new space development for someone from old space / old boys network.
We really do need a fresh start - the more I poke at this the worse it looks.