Living in Hilo, and working on Mauna Kea, I think the administration of UH-Hilo would have heart attacks if they were ever approved to do anything involving the word "billion." They're constantly struggling to get funding for things like a permanent building for their pharmacy Ph.D program (which would help quite a bit with continuing accreditation). No, the TMT isn't a UH-Hilo project, at all.
It's actually University of California and CalTech (the main partners in Keck), plus ACURA (the Association of Canadian Universities for Research in Astronomy, not Honda's sporty brand, sorry), Japan, China, India, the NSF, and maybe whoever else wants to jump in at this point now that things are approved. A mere $3.57 million might be enough to get yourself a 1-night-a-year slice of the pie. ;)