Run Facebook or Instagram ads to a retreat and see visits, checkouts and paid bookings for each ad, plus cost per booking.
Open the event (Events → the event). In the Ads section, click "Copy URL parameters for Meta ads". The Website URL is the link to the event itself ("Copy link" at the top of the same page). The Ads section sits at the top of the page once your Meta Pixel is connected or a booking has come from an ad, and below the bookings list until then.
In your ad, put the event link in "Website URL" and paste the copied text into "URL parameters". Meta then fills in Facebook or Instagram, the campaign name and the ad name on every click, so nobody types them.
Click "Full report" in the Ads section, or go to Analytics → Ads & sources. It shows visits, people who started checkout, paid bookings and booking value by source, and by campaign and ad.
With one event picked, click "Add" next to Ad spend and enter the amount. The report then shows return on ad spend and what each booking from ads cost you.