I looked into the San Diego tunnel. They suggested getting in touch with an org that's doing group sessions.
$975 for your turn.
Near as I can tell it's around $5-7k a day, if you figure in the group's profit margin.
I'm still interested in doing a session, the last date they had was conflicted for me and they don't have any new dates up yet.
Here's the link:
http://www.multisports.com/windtunnel_camp.shtml