There are a lot of factors in your dilemna. I have installed a wireless infrastructure 802.11 super g, for a 60,000 sq foot facility. which required two repeaters and three access points, some electrical runs and a couple of days to configure. The facility had several internal concrete structures and firewalls. The cost for equipment and installation was about $5,000 including labor. The equipment was Netgear and only cost $2,000 of that $5000. The rest was labor cost.
For a quarter of a Billion dollars, I would get a couple of other vendors in to do site surveys and capacity planning. Antenna placement, coverage areas, connectivity standards, security, etc. will all have a pretty significant impact on the cost.