The excellent article posted by Brian earlier had the kicker line:
"Defence - never keen to reject already-committed funds - went ahead and signed the $660 million helicopter contract with Kaman."
A couple of decades in Defence exposed me to the general idea that committed funds nearly always got used for the 'approved purpose' (usually approved after arduous, lengthy and involved process and signoff), or the funds would be snaffled for another project. The trick in Defence is to get any project enough momentum and support by key staff to bubble up into the realm of consideration, then see where is goes. Once all the politics and approval is achieved (often years), the easy part is to start it off! However if the funds get gobbled up in development costs and there is not enough left for the final job, the politics of face-saving make cancellation (or downsizing) are far less risky than grovelling for more money (especially close to an election!)
The PC9 fleet avionics upgrade was a case in point....the system was developed and prototype flown, then the money not enough, an election was looming, so the project was amended to just do a couple of airframes and the fleet forgotten. Oh and all the parts were bought and are sitting on the shelves!