Do the p_ fields such as p_event_time, that Panther automatically adds, count in the total size of logs the customers are billed for?
These additional p_fields do not count in the total size of the logs the customers are billed for. It is the uncompressed data sent that are included.
These fields are our Standard Fields, as mentioned in our documentation.
The following relevant articles from our Knowledge Base might be useful, as they provide additional context on the ingestion limits: