Development teams often use mental models to simplify development time decision making because a comprehensive empirical assessment of the trade-offs across the metrics of development time, development costs, proficiency in market entry timing, and new product sales is simply not feasible. Surprisingly, these mental models have not been studied in prior research on the trade-offs among the aforementioned metrics. These mental models are important to consider, however, because they define reality, specify what team members attend to, and guide their decision making. As such, these models influence how development teams make trade-offs across the four metrics to try to optimize new product profitability. Teams with such an objective should manage to a development time that minimizes development costs and to a proficient market-entry timing that maximizes new product sales. Yet many teams use mental models for development time decision making that focus either just on development costs or on proficiency in market-entry timing. This survey-based study uses data from 115 completed NPD projects, all product line additions from manufacturers in The Netherlands, to demonstrate that there is a cost to simplifying decision making. Making development time decisions without taking into account the contingency between development time and proficiency in market-entry timing can be misleading, and using either a sales-maximization or a cost-minimization simplified decision-making model may result in a cost penalty or a sales loss. The results from this study show that the development time that maximizes new product profitability is longer than the time that maximizes new product sales and is shorter than the development time that minimizes development costs. Furthermore, the results reveal that the cost penalty of sales maximization is smaller than the sales loss of development costs minimization. An important implication of the results is that, to determine the optimal development time, teams need to distinguish between cost and sales effects of development time reductions. To determine the relative impact of these effects this study also estimates the elasticities of development costs, new product sales, and new product profitability with regard to development time. Armed with this knowledge, development teams should be better equipped to make trade-offs among the four metrics of development time, development costs, proficiency in market-entry timing, and new product sales.