Coal, smelts ores, makes torches, comes, has a good smelt exchange, can be traded with villagers, powers engine carts, etc.
?? We? What? Price? ?? It seems the most valuable (per item) renewable resource on EMC at the moment it is Wither Skull.
If you're looking for something on that list - wither skulls are most valuable per item. Personally, mob drops I don't really consider as renewable in the sense that you have to go to where the mob spawns and hope. I would say charcoal is the most valuable renewable from your lot resource. Growing trees and burning the wood gets it quick.