The Hubble has returned a tremendous amount of new astronic discoveries. It has also cost a fortune to build, maintain, and operate. Just the Shuttle mission costs alone to support Hubble probably add up to a couple billion dollars. Add in the billion+ dollars it took to build Hubble in the first place and the support costs and the total is probably somewhere around $4 billion, maybe even more.

I got to see the Hubble before it was launched. I was visiting the Lockheed plant in Sunnyvale, CA while TDY to the "Blue Cube" at Onizuka AFB. The Hubble is big, about the size of a city bus. It was supposed to be launched in 1986 but was delayed by the Challenger accident. It turns out is wasn't nearly ready for flight in 1986 and needed several more years of work before being launched in 1990. Too bad no one would pay the estimated $50 million it would've cost to fully check the mirrors before flight. They would've saved several hundred million dollars in repair costs and given us 2-3 more years of good data.