I certainly do not begrudge the efforts that go into building the shuttle software the process they must follow to ensure their code remains at such a high level of quality. When you have essentially an unlimited budget you can achieve a lot with competent managers, staff, and a process that is well-defined and understood and, most importantly, enforced. I don't know the details here but I'd be willing to bet that the cost of developing and maintaining their code greatly exceeds that of the vast majority of successful software efforts on a per line of code basis.

It gets back to the old saying: Cheap, Fast, Better. Pick two.