Why did they make people pay? That doesn't make sense.
$300 attendance fee was probably just about right. A conference of this type is intended to build up the network of the bitcoiner community, get business people talking to each other about ideas and projects, problems and solutions in bit-commerce. Concrete business deals would get struck.
A cheap event would allow in many people who are interested but never plan to do anything constructive. They would learn, but that can be done remotely, online.
Signal not noise!
I think free and VIP options would be best. Maybe brochures and stuff like that at stalls for free people, then VIP gets the seminars and a VIP room or something.
Then you get the best of both worlds. Some people can come by just to see what bitcoin is, while some come to collaborate with others and learn deeper concepts.
Too many non-movers undermines the point of the conference. You need the right number of the right kind of people for the conference to be a success...and success is not measured in # of attendees or ฿ collected in conference fees. The goal of the Bitcoin Foundation holding the conference is to advance Bitcoin and hopefully not lose money on the event. In fact, if I recall correctly, in the early days there was talk of "hoping to break even."