http://www.space.com/news/hubble_mission_040810.html

The robotic mission to save Hubble would cost up to $2 billion, several
times what a human-run Shuttle mission would cost. I predicted this and I'm
wondering if it wouldn't be more prudent to make an exception for Hubble and
ignore the safety rules.

OTOH the success of a robotic mission would be a quantum leap for
teleoperated serviciing in space.