To bulk edit existing product prices only, got to the Products page, tap 
then Export Price File to export basic product information and prices across all sales channels.
Important: Only the Cost Price, Price and On Sale can be edited then re-imported. The remaining data is to provide context about each product.
If you have multiple stores, you will be able to edit the prices individually for each store.
Once the prices have been updated in the CSV, the prices can be re-imported and updated. Tap then Import, to import the changes.