The exemplary embodiments provide medicament delivery devices that use cost functions in their control systems to determine medicament dosages. The cost function may have a medicament cost component and a performance cost component. The exemplary embodiments may use cost functions having medicament cost components that scale asymmetrically for different ranges of inputs (i.e., different candidate medicament dosages). The variance in scaling for different input ranges provides added flexibility to tailor the medicament cost component to the user and thus provide better management of medicament delivery to the user and better conformance to a performance target. The exemplary embodiments may use a cost function that has a medicament cost component (such as an insulin cost component) of zero for candidate dosages for a range of candidate dosages (e.g., below a reference dosage).