You can quickly see a revenue report by heading into your Inventory, clicking on an item, then moving into the Usage Tab.

From here you can select which date range you'd like to explore and you'll receive a bird's eye view of how the item is performing.
 

Here's a breakdown of all the information that you are receiving in this report:
Gross Revenue: The gross revenue this item has earned during the selected time period.
Percent of Category Revenue: The percent of the item's category revenue this item accounts for.
Projects: The number of projects this item has been on.
Min / Max: The minimum and maximum revenue this item has earned on a project.
Average per Project: The average revenue this item earned across all projects
Gross Category Revenue: The gross revenue this item's secondary category has earned.

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