I think you'd be hard-pressed to get a scientist to admit that the money was lost. ;) 

Honestly, it's not obvious that it would have been possible to do Advanced LIGO without the experience from the initial run, which is kind of the point I was making: we don't usually have tasks that humanity needs to get right on the first try, to the contrary humanity usually needs to fail a few times first!

But the initial budget was around $400 million, the upgrade took another $200 million. I don't know how much was spent operating the experiment in its initial run, which I guess would be the cleanest proxy for money "wasted", if you're imagining a counterfactual where they got it right on the first try.

I signed up just to comment on this:

"The LIGO gravitational wave detector probably had to work right on the first build, or they'd have wasted a billion dollars. It's not like they could've built a smaller detector first to test the idea, not on a real gravitational wave."

LIGO did not work right on the first build. The original LIGO ran from 2002 to 2010 and detected nothing. They hoped it would be sensitive enough to detect gravitational waves, but it wasn't. Instead, they learned about the noise sources they would have to deal with, which helped them construct a better detector that was able to do the job. So this really isn't a good example to support the point you're making.