If you have added line items from your price books onto a favourite, then the standard pricing for them will update with changes to that price book item.

For example, if I add a line item from my custom price book into a favourite, then change that item's cost price when editing my custom price book the favourite will also update to use that new price.

In a similar vein, if I upload a new price file CSV from a supplier, then the standard pricing will also update for any of those line items in the favourites as well.

However, if you change the line item's name or description in your Favourites, future changes to the price book will not update the Favourites but add new line items.