Free conferences be like:

"Delegates agree to attend one-on-one business meetings and other group activities. You must attend all pre-booked meetings and sign the meeting registers. Non attended meetings will be charged at the full cancellation rate of £495 + £195 per non attended meeting."

https://shkspr.mobi/blog/2020/03/it-will-cost-you-500-not-to-attend-this-conference/