Note that NASA encourages its contractors to use their stuff for private missions as well—building more of the things reduces unit price (by amortising developm

Note that NASA encourages its contractors to use their stuff for private missions as well—building more of the things reduces unit price (by amortising development cost) and thus costs for NASA, so it could be that this results in lower overall cost to US taxpayers. In addition it helps collect more data on safety etc, which is in NASA's interest, too.