These costs are calculated based on buying the unfinished potion premade. This allows you to skip putting clean fellstalks in a vial of water. However, this method is more expensive. The extra loss accumulated via this method is -1,198 per potion, however, the experience per hour is doubled.
The profit for making an unfinished fellstalk potion using either a vial of water or filling your own vial is as follows.