I can think of one Earth orbiter that had to take a dive because of funding...The Compton GRO had a couple of good instruments on board that were still good, but it burned up in the atmosphere due to lack of funding to keep it up there. BATSE was integral to the Gamma Ray Burst sub field at the time, too. It was the only all sky burst detector in existence at the time, and was instrumental in detecting some of the first optical counterparts to Gamma Ray Bursts.
I think only now there is a replacement, 2 years after it burned up. HETE-II has an all sky detection system as well.
Gamma Ray Astronomy, where one photon really is worth few thousand dollars.
That was a disgrace, but I heard that we deorbited it as an example to encourage the Russians to deorbit Mir.