Rather than repair it in space, would it be easier to bring it back to earth, refurbish it and relaunch? That would be $120M plus refurbish costs. Or am I underestimating how hard it would be to bring it back to the ground?
The key thing to remember when it comes to space is energy/momentum. Right now, the Hubble Space Telescope is 24,000 lb of mass moving at 4.7 miles per second. To get it back down to earth, you need to somehow slow it down. First, slow it down enough to reach the atmosphere and then protect it as the atmo drag slowed it the rest of the way. I don't even think the Space Shuttle, were it still around, would be capable of doing that.
The only thing that was ever designed to bring substantial mass back from orbit was the Space Shuttle Orbiter, which is decommissioned. Even then, I'm sure Hubble was not designed to fold back up and fit into that cargo bay.
I think it's instructive that they never tried that with any of the earlier Hubble repair missions.
At that point you’d just launch a new one. Earth’s gravity well assesses a steep tax.