http://world.episerver.com/documentation/developer-guides/commerce/pricing/

Values edited via the optimized service are immediately incorporated into the detail service. If a custom optimized service is implemented, and it does not have its own mechanism for synchronizing with a custom detail service, the detail service must call IPriceDetailService.ReplicatePriceServiceChanges on edits to update the optimized data store. When you replicate optimized prices into the detail service, values for the edited catalog entries are replaced in the detail service, which may eliminate redundant values or create less intuitive data when price values are split. For this reason, use the price detail service as the service to use for editing, unless this behavior is specifically desired.