According to NASA web pages, it costs $450 million per launch. Of course that does not cover other costs like training, capital expenses (new equipment from time to time), and (I suspect) the operating costs of a mission after launch.
As a former engineer, I admire the shuttle. As a taxpayer, I'll be happy to see it replaced by lower cost expendables or semi-expendables like the Falcon.
The shuttle was originally touted as a way to reduce the cost of space travel. Since that didn't work out it it became a way to continue our manned presence in space. Our manned presence in space was necessary to operate the space shuttle, a nice piece of circular reasoning.
One popular bit of reasoning was that without the shuttle we couldn't have fixed the Hubble telescope, but without the shuttle we could have had the money to build a new one, or maybe two.