If only one aspect can be measured, what should it be according to DA?

Cost of delay is emphasized in the Disciplined Agile (DA) approach as a critical metric because it reflects the economic impact of not delivering a product or feature timely. This metric helps teams prioritize their work based on the value that could be lost by delaying delivery. Understanding the cost of delay enables teams to make informed decisions about which features or tasks to focus on, aligning their efforts with delivering maximum value to stakeholders as quickly as possible.

In a project context, while total project cost, team performance metrics, and customer satisfaction scores are all relevant markers, they do not directly provide insight into the urgency and impact of delivery timelines in the same way cost of delay does. By concentrating on cost of delay, teams can create a more adaptive planning environment that emphasizes speed to market and responsiveness to customer needs, which are essential elements in agile methodologies.