> When the components NASA needs are available off-the-shelf, that will be an excellent approach.
The actual spacecraft is about half the cost of any NASA program. The other half is all the test equipment, the prototype models, etc.
Having worked on the Kepler program, I can assure you that there are many off the shelf components that can be used -- not necessarily on the spacecraft, but definitely in the test equipment area. Another effort that the contractors are scurrying to implement are reusable test components that can be carried over from program to program. The difficulty is that most NASA contracts state that all the equipment created over the course of the program belongs to NASA. Figuring out the legal bits of the contract to make equipment reuse more viable is another change that needs to happen at NASA/JPL, too.