According to the PSPO II guide and Scrum.org competencies, when ordering Product Backlog items, a Product Owner should consider various factors to maximize the value of the work done by the Scrum Team. These factors include:

A. Dependencies to other products: Recognizing dependencies to other products is crucial for the Product Owner to ensure that the Scrum Team is working on items that can be completed and deliver value without being blocked by external dependencies.

B. Value of Product Backlog items: The primary role of a Product Owner is to maximize the value delivered by the Scrum Team, and ordering items based on their value is a fundamental aspect of this responsibility.

C. Dependencies between Product Backlog items: Understanding and managing dependencies between Product Backlog items helps in planning Sprints more effectively, ensuring that the team is working on items in a logical sequence.

D. Cost of delay: The cost of delay is a critical economic factor that influences the ordering of Product Backlog items. Items that would result in a higher cost if delayed should be prioritized.

E. Cost of implementation: While value maximization is the goal, the cost of implementation cannot be ignored. Balancing the cost and the expected value is essential for effective Product Backlog management.

These considerations are in line with the Scrum.org Professional Scrum competencies, particularly under 'Managing Products with Agility', where it's emphasized that Product Owners should have a deep understanding of market value, product feasibility, and the importance of making trade-offs to maximize value.