I’ve managed paid and free events. For paid events, drop-out rates are natural significantly lower but ensuring payment in advance is vital. For free events, depending on the target/location/historical data, I have adopted an add 35% to the target number to work on a 35% drop-out. At the end of the day, if an event is free, it’s tricky as there are no repercussions to the individual if they drop-out. Content is key.
I attended a free event recently. I was pushed for time and ideally would have dropped out, but the topic (GDPR for small businesses) and the speakers (industry leaders) made it a must. It was a packed out!