How much do Silicon Valley venture capital firms spend on developing
their Web sites? My guess is that they spend $10-20,000, but I would
like to get some proof of this. (I would also appreciate the names of
the Web design firms that these VCs employ.) Thanks.

I can't give you proof, but the VC sites are not all that hot.  They
don't get business that way.  One exception was Divine which was
pretty cool, though the firm itself is gone.

Based on the fact that they don't need to build awesome sites, 10-20K
is a good guess.