The market is a complex system with many different stakeholders and interactions. A number of decisions within this system affect the design of new products, not only from design teams but also from consumers, producers, and policy-makers. Market systems studies have shown how profit-optimal producer decisions regarding product design and pricing can influence a number of different factors including the quality, environmental impact, production costs, and ultimately consumer demand for the product. This study models the ways that policies and consumer demand combine in a market systems framework to influence optimal product design and, in particular, product quality and environmental sustainability. Implementing this model for the design of a mobile phone case shows how different environmental impact assessment methods, levels of taxation, and factors introduced to the consumer decision-making process will influence producer profits and overall environmental impacts. This demonstrates how different types of policies might be evaluated for their effectiveness in achieving economic success for the producer and reduced environmental impacts for society, and a “win-win” scenario was uncovered in the case of the mobile phone.