Cost of Delay is the value you lose for every week a feature isn't shipped. It asks a simple question: if we don't ship this for another week, what does that actually cost us? Not in vague "missed opportunity" terms, in dollars, churn, or competitive ground lost.
Don Reinertsen popularized the concept as part of lean product development. Delay has a price, and that price stays invisible until you make it explicit.
Why it changes prioritization
Most teams prioritize by effort. A quick win that nobody cares about is still a waste. Cost of Delay flips the lens, you start with value at risk, then compare it to how long something takes.
That ratio is called CD3 (Cost of Delay Divided by Duration), and it's one of the most honest prioritization signals you can calculate.
Example: Feature A takes 4 weeks and loses $10k/week of value by waiting. Feature B takes 1 week but only loses $5k/week. CD3 for A is 2.5, CD3 for B is 5. Ship B first, even though A sounds bigger.
Making the estimates
You still have to estimate delayed value, which is hard. But rough estimates beat gut feel. "Somewhere between $5k and $20k per week" is more useful than "it feels important."
If you're using a roadmap to communicate priorities, Cost of Delay gives you something concrete to point at when stakeholders ask why one thing is above another.