The value of any NFT, as much as it is for any collectible, is subjective and it might not be possible to fit it into an equation. However, certain factors like the rarity of the NFT, the person launching it, the asset/collectible it represents, and the profile of people owning other similar NFTs are known to increase the value.
For example, an NFT featuring the greatest and legendary comic character creator is bound to fetch high value, both at launch and in secondary marketplaces.