WooCommerce is a powerful plugin capable of handling small and large stores. If you have too many products, making price changes one item at a time will not be the best way to use your time. The Excel-Like Price Changer for WooCommerce lets you make changes to your product information as you would in a spreadsheet.
The Light version lets you make changes to your prices. The pro version gives you more flexibility editing, importing and exporting to CSV. Up to 20 custom fields are supported. This plugin is also compatible with WP E-Commerce. You can try it here.