Price Rules for tickets and Scheduled Items can feature different behaviors when the Create Contact for Attendee setting is in play.
Create Contact for Attendee is an optional Contact/Attendee setting under Event Info in the Event Builder. When it is enabled, a Contact record will be created for a guest if no Contact record is detected for the guest. We recommend having the setting Enable Contact Search (also located under Contact/Attendee Settings under Event Info) in use to avoid creating duplicate Contact records.
How does this setting affect Price Rules?
When a Price Rule for an event ticket or Scheduled Item applies to the registering attendee, that Price Rule can also be unintentionally applied to any guests the registering attendee has included if Create Contact for Attendee is not enabled.
To make sure the Price Rule is not applied to any of the registering attendee's guests, enable Create Contact Attendee (and Enable Contact Search) in the Event Builder when creating the event.