Backlog priority is a product owner responsibility. Agile technique state that priority must focus on deriving maximum benefits. However, there are many perspectives that a product owner can learn to derive the benefits. These are some quick practical ways to derive maximum benefits for your backlog priority.

Align Product and User Value
All users view maximum values from their perspectives. This is why backlog priority must never be provided from only the user view. Product owner must always match user values with the product values. You should not seek to please the users but look at the overall product. This is a simple rule of thumb, yet difficult to negotiate for backlog priority! The key is to align these values to a common ground. This will take a lot of practice for product owner and you must not get discouraged by unreasonable users.
Is the Story Logical?
Story mapping is a good technique to review the product and user values. There will be a good logical flow for a good story. A disconnected story will indicate a lower value. Some story appear as exception scenario and this will order it to the bottom of backlog. Thus, the story points or logical importance will help you to determine the backlog values. Subsequently, this will order your backlog in a logical sense.
Backlog priority is one of the fun moments of product owner. It will take a lot of practice to prioritise the backlog for maximum values. Agile do not provide a clear hard rules for backlog priority for a good reasons. As product owner, you will know what is maximum value and order your backlog in a clear manner. Of course, product owner decision is final and there can be only one!