Space Shuttle Endeavour, the replacement orbiter for Space Shuttle Challenger , cost approximately $2.1 billion.
That was actually a good deal cheaper than the original estimates, because it was made primarily of replacement parts for other shuttles. We don't have the extra parts to do that now and still have enough parts for the rest of the fleet. So a new shuttle built to the same specs as the others would cost more since almost all the parts need to be fabricated.