Truly "black" projects have enourmous security costs that make everything more expensive. Being black, they can also avoid the oversight that other projects receive. Still, the black projects that I've learned about have a pretty good track record overall.

Consider the U-2, a black project from the 1950s. It went from contract signing to first flight in 10 months. It was on time and budget. How about the Blackbird? There were some significant engineering challenges that did drag out that program like having to develop completely new machining technology to work with titanium. That project took about 3-4 years.

Read Ben Rich's book "Skunk Works" about the development of the F-117A. Despite security requirements only equalled by the Manhattan Project, in the end the F-117A came in on time and _under_ budget. There was one point where Lockheed was going to have to refund leftover money but the Air Force used that for upgrades instead.

Contrast that with NASA's track record.
Apollo - on time but grossly over budget

Viking - on time but way over budget

Shuttle - years late, over budget, and never met the specs for turnaround time or payload to orbit.

Hubble - years late, over budget, and required an expensive repair flight to make it work. You'd think in all those years when it sat on the ground waiting to fly (following Challenger), someone would've thought to check the optics.

Galileo - late (partially due to Challenger), over budget, and the loss of the high gain antenna really reduced the amount of data the mission returned. The data it did return is very good but it's probably only a few percent of what would've been returned had someone bothered to check the antenna before launch.

GOES-Next - years late, over budget

Chandra - ditto

ISS - need I say more.

The fact is, I don't know of a single big NASA project that ever came in on time, on budget, and met the requirements. That's a pretty dismal track record. NASA seems to do quite well with smaller projects like Mars Pathfinder and the X-38 but it seems the bureaucracy doesn't seem to have what it takes to do the big things.

Other government projects also have their share of problems. Consider the "Big Dig" in Boston. It was supposed to cost somewhere around $2 billion. The last I heard, the price is over $13 billion and rising. Consider the Reagan Office Building in DC that is costing over a billion dollars. Consider the mini-temples of federal office buildings and courthouses around the country. Those also have a sad record of overruns and excesses. Even the National Park Service paid over $250,000 a few years for an outhouse in one of the parks.

Now consider projects that aren't government contracts. For example, at the same time McDonald Douglas was struggling to keep the C-17 wings from failing below requirements and the empty weight under control, the same company also managed to build the MD-11 on time and on budget. It seems companies are more careful with their own money. Imagine that.