don't let a distinct drop in posting get to you. Seriously, if it were the middle of June and people weren't posting much or paying, THEN that'd be a huge concern. People who plan for an event like this typically worry about travel and housing costs the most and see that as the main expense to handle early. something like the entrance fee, in their minds, can wait and will have to until they get more money together.
No need to draw conclusions so quickly. A lot of people who intend to go who haven't paid probably won't post again until they have paid. It's a weird guilt thing....but anyway, I hope my optimism isn't misplaced >_>