You want find the lifetime revenue of an item. In order to do so, please follow the steps below.
Enter the "Analytics" tab on Renterra and then press "View Ledger" in the top right corner.
Filter in the top right hand corner for the Rental Revenue account and Item you are interested in (you will have to filter for Sale Income if it is a Sale item)
Click the "Export" button at the bottom of the table and sum up the net Credits - Debits for the item