It is not guaranteed that the projects will be implemented. All four are part of a recently established Pioneers program that promises to help relatively new researchers conduct experiments, but only until the mission fits below the $ 20 million limit. While this is cheap compared to many NASA missions, there is a chance that the newly chosen concepts will lose if they exceed the budget.
However, this challenge is part of the question. Ideally, NASA could not only do more astrophysics research than limited funding, but also promote more creative ways to conduct science. This could reduce its dependence on conventional satellites and the giant rockets used to launch them into orbit.