The NRO instruments are just optics, optics make up a tiny fraction of the cost of a space telescope. NASA was not gifted fully functional space telescopes they

The NRO instruments are just optics, optics make up a tiny fraction of the cost of a space telescope. NASA was not gifted fully functional space telescopes they could just launch and then start observing. They still need all of the components to actually turn them into functional instruments, spacecraft systems, cameras, attitude control, etc. The estimated cost for WFIRST alone is $3 billion, only slightly less than if the instrument had been built from scratch, if at all.