If updating a price list in a CSV , the "Update the current price list" checkbox MUST be selected in order not to duplicate the price list. That checkbox being checked by default would mitigate this risk and save Support and Build teams a HUGE amount of time.
For example, if new items are being imported in a price list CSV, and the checkbox is selected (but doesn't need to be for this process), the import just doesn't go through - not a problem.
BUT if the existing items in the price list are being updated in a CSV and that checkbox is not selected, a 400 item price list turns into 800 items and the duplicated items have to be deleted manually one at a time.