I don't have access to the game right now but I believe the "value" listed in the Wiki is the price that you would sell an item to a vendor for (as opposed to what you'd spend to buy the item). So, if you skinned everything yourself and then had a choice of either selling the raw materials directly to an NPC vendor or turning them into a leather shirt, you'd make more money just vendoring the skins. Or, more accurately, you'd make the most money buying some tannin powder from a vendor, turning the skins into rolls and then vendoring the rolls (3 councils profit vs just selling the skins, whee!

) . If you continue processing the materials to actually make a shirt, you lose money compared to either the skins or the rolls option.