I'd pay $15 per day
I think there is a real difference to events which are free and ones you need to pay to get into. The challenge to put on a free event for everyone is much greater and speaks alot more about what the event is trying to convey.
Putting an entrance fee on it could result in a drop in attendance. Only the real fans of the music will go and many of the "raver kids" just looking for some music to practice their breakdancing skills to would shyaway from it (possibly).
