Managing the product backlog and prioritizing the user stories if one of the main responsibilities of the product owners in Scrum. In this blog post, Andy Carmichael explains how to assess the priority of product backlog items using the cost of delay.
The cost of Delay is the cost to bear as a result of delay in investment. Andy Carmichael bases his analysis on David Anderson’s Kanban book that proposes four archetypes to categorize the costs of delay, plotting on a chart the impact (opportunity cost) against the time of release. Using this type of charts with an example, the blog post explains how you can assess this cost of delay. You can then decide if your item is an expedite item that have a high cost of delay and should be started immediately or a fixed date items have a high cost of delay only once a threshold is passed.
Read the complete blog post on http://xprocess.blogspot.com/2013/04/selecting-backlog-items-by-cost-of-delay.html