The subsequent repair missions have keep it in operation a lot longer than would have been possible otherwise (replacing failed gyros, failed electronics, orbit boosting), plus the ability to put in new technology instruments has to have been very valuable. And the ability to put in instruments for a limited time, i.e. ones that could be justified for a period between maintenance missions but not for the lifetime of the whole thing.
Robots have their place and so do men.
I pointed out just one example contradicting the last two points. Trying to apply the whole cost of the Shuttle program to just this one project is not to the point, nor is implying that we couldn't have done it in a manner that cost less and was safer.
As an incremental cost, assuming you have a manned space program, you can't justify doing robotic repair due to the extra costs and limitations.
On the other hand the next big telescope project (http://en.wikipedia.org/wiki/James_Webb_Space_Telescope) will be non-repairable, but that sort of goes with its mission, which is to sit at the Earth-Sun L2 point. Design life of 5 years, they hope it'll make it to 10. Note that the Hubble has made it to 20 years and they expect it'll last at least another 4.
And I'll certainly agree with you that if you want to explore beyond Mars for now, do it with robots. And to put humans on the Moon or Mars, send robots first (as we did for the Moon and are doing for Mars).
On the other hand, if I wanted to thoroughly play with an asteroid, I would want to do it with a manned mission (after suitable earlier check-out by robots).