Upon death, a monster may generate one or more of several different body parts. These are listed below in order of decreasing rarity.
The base value of all body parts is `600 + 40*monster_level`, but sale value caps out at 33%, which effectively makes the formula `200 + 13.333... * monster_level`. Numbers after the decimal point are truncated.
There seem to be enemies that don't follow this formula exactly, however - gold bells and bards, while relatively tame foes, drop parts that sell for quite a bit in comparison to other enemies of equal level. [confirm?]