In addition to the tables below, almost every creature will have an essence. The rarity of that essence is determined by the DM based on the difficulty of the creature.
Supply & Demand. Due to the prevalence of beast components, trade values are reduced.
Extraplanar Recall. As the bodies of celestials disintegrate upon death, shunting their souls back to their home plane, only pouches of dust can be harvested if the creature is killed anywhere other than its home plane or in a magic circle.
Supply & Demand. Due to the rarity of celestial components, trade values are increased.
Supply & Demand. Due to the rarity of draconic components, trade values are increased.
Extraplanar Recall. As fiends’ bodies disintegrate upon death, shunting their souls back to their home plane, only pouches of dust can be harvested if the creature is killed anywhere other than on its home plane or in a magic circle.
Supply & Demand. Due to the low demand for humanoid components, their trade values are significantly reduced. In fact, it’s unlikely any respectable establishment will carry them.
Hard Bits. When an ooze dies, the DM will roll a d100 and consult the Ooze’s Random Components table to determine what random component the Ooze previously consumed and has left available to harvest.