Answer
The point of Mark 8:36-37 is not to describe the exact value of a soul, but to point out the subjective value of a soul relative to the value of the world in the experience of each individual.
Jesus was saying that no matter how great your earthly goods, enjoyment, and satisfaction are in this life, you yourself will find that they are not as important and valuable as the life you will have after you die. It is not that the eternal fate of one soul is more valuable than all the world's goods and blessings as experienced by all people in the world combined. Rather, it is that the experience of these goods and blessings by one individual in this life is less significant than the eternal experience of that same individual, whether that eternal experience be good or bad.
In other words, no good experience in this life is so valuable that it is worth trading your eternal blessedness to gain, and no bad experience is worth trading your eternal blessedness to avoid. Conversely, all earthly good is worth trading to gain eternal blessedness, and all earthly troubles are worth enduring for the sake of gaining eternal blessedness.
Answer by Ra McLaughlin
Ra McLaughlin is Vice President of Finance and Administration at Third Millennium Ministries.