And two city-states competing for the same natural resource will share it with each other in enlightened cooperation? No, that isn't how the primate territorial instinct works.
Assuming we are talking about city-states of problem solvers. Than they will neither compete nor cooperate. They will just pay the market value for a barrel of oil.
Instead, the fierce and low-margin/high-risk compitition actually exist between aggressors 1. for the control of same region (eg Saudi Arabia) and, 2. providing same product (eg crude oil).
