Gus is set on controlling the market for meth in the Southwest. He has worked hard to eliminate the local drug cartel so that he can be the sole supplier. Being the only supplier of a product gives a firm market power to charge prices greater than marginal cost. While profit maximization still occurs where marginal cost equals marginal revenue, a firm with market power is able to charge a markup on top of the marginal cost. Further, the markup is inversely proportional with the price elasticity of demand coefficient (i.e. the more inelastic the demand, the higher the markup). As the number of substitutes (competitors) decreases, the demand for each firm becomes more inelastic, which, in turn allows the firm to charger higher prices.
See more: market power, game theory, monopoly, strategic behavior, market structure