You can delete prices in bulk for any price list by going into Inventory > Price Lists > select the Price List to edit > select the Variants you would like to delete the prices for > from the Bulk Actions menu, select Remove from Price List. This will remove the prices for the selected products from the price list. If you have high number of Variants you need to delete the prices for, you can do this via CSV. From the same price list page, click on Update Price List via CSV > Build and Download the CSV template for the price list > clear/delete the prices for the products as required > Save and re-upload the CSV within the same page.