To be fair, they did this with Godiva festival in Coventry to good effect - It's a public music festival put on by the council, however every year there were issues with overcrowding and people queueing to get in after the venue reached its capacity.
They changed the model to ticketed entry at £3 per person (enough to pay for the full infrastructure for collecting and checking tickets but nowhere near enough to scratch a surface on the event costs) and it worked really well - no queues and really good value. The money wasn't a barrier to entry, but did put up enough of a barrier to entry to mean that people didn't register 'free' tickets and then not show.
They changed the model to ticketed entry at £3 per person (enough to pay for the full infrastructure for collecting and checking tickets but nowhere near enough to scratch a surface on the event costs) and it worked really well - no queues and really good value. The money wasn't a barrier to entry, but did put up enough of a barrier to entry to mean that people didn't register 'free' tickets and then not show.