The booking price will be recalculated when rescheduled or the quantity is changed.
The recalculation will use the, at that current time of the change resource price - thus losing whatever custom price set for the booking originally.
For rooms the recalculation of the booking price will occur when one of the following things is changed for the booking:
The start or end time of the booking is changed (booking period)
For catering items the recalculation of the booking price will occur when one of the following things is changed for the booking:
Start time (time of delivery)
Quantity (number of items in the booking)
Associated delivery services and extra services will also be recalculated, since they are related to the booking of catering services.