$900 million would go a long way in paying for Hubble II
Imagine a telescope built along the same design, but with a 3 meter (nonflawed) primary mirror instead of the 2.4 meter mirror on Hubble. That would allow a significant increase in light gathering capability without a massive increase in size. It would be an evolutionary design with all of the lessons learned from Hubble over the past 16 years incorporated into it.