My name is Alison, and I'm the Customer Success Specialist for Ablestar apps. You can also use our Bulk Editor app (https://apps.shopify.com/bulk-product-editor) to modify the prices, and it is much quicker and easier than exporting a spreadsheet and editing it (although that would work). Using the app, you have the ability to modify the price and compare at price in the following ways:
Price Edit Options
The app also has a free version that allows for 5 free in-app edits and 5 free spreadsheet edits a month, so you could try it out without incurring any costs.