Obviously the private sector is able to undertake large, expensive, and dangerous projects. The Great Northern Railroad, ocean liners, steel mills, mining operations, offshore oil-drilling platforms, and nuclear reactors are all examples of this. What Dr. Tyson is really saying is that he doesn’t think the private sector would allocate resources the way that he and his fellow astrophysicists would want it to - i.e., he thinks it would allocate less to them and more to other things. But that would be up to the private sector, wouldn’t it?