Well I looked around and i saw where they were anywher from like $50 to $300 depending on diameter, ports, and if you wanted shutoff valves built in.
http://www.houseneeds.com/shop/plumbing/pexplumbing/vanguard/pexmanifoldsbuypage.asp
http://www.houseneeds.com/shop/plumbing/pexplumbing/vanguard/pexmanifoldsbuypage.asp