There are two effects on our ability to deliver value when we have these roles in place, and the people doing these roles operate as intended:

1. With a great Scrum Master, the team is able to deliver more: The team operates at a higher capacity than what each of the individuals on the team represents. For example, it is not uncommon to see improvements of 2X, 3X, even 5X over what the individual capacity of team members would indicate. If we have team made up of 8 people and they are operating at a 2X level as a result of coaching, then they are behaving like they are a team of 16 people from the perspective of their ability to deliver.
2. With a great Product Owner, the team is able to deliver more of the right kind of value: The Product Owner takes the input from the customers (is the voice of the customer), the business, other stakeholders (such as other teams, management, and so on) and creates a force ranked list of what is needed to be delivered by this team; a backlog. The team operates by pulling items from the backlog starting at the top of the list. All work comes from the backlog - there is one list. In this way we have a clear view of the value we need to deliver and can help the team focus on the most important thing.

By having great Scrum Masters and Product Owners we are able to deliver more value faster

Better and more value delivered; not a bad return on your investment for identifying a Scrum Master and a Product Owner.