Hi Kate!
I’m sorry you are having that issue. Let me help you troubleshoot that.
Are you getting those $0 cost only in the checkout or also when viewing the event? Is there a difference between the cost of a ticket when editing an event, and ticket product from WooCommerce?
Does it happen for all tickets/events or just some? Could you please share a link to that event with us so we can see if we spot any issues?
Also, this could be related to a plugin or theme conflict, so could you please go through the complete steps in this guide > https://theeventscalendar.com/knowledgebase/testing-for-conflicts/ and let me know what you can find in the process?
Thanks,
Victor