This is Rae from Shopify. Thanks for posting this question - I'd love to lend a hand with this.
There are a few different methods that can be used to change the pricing of products, such as using the bulk editor, or a product CSV to update each price. The bulk editor will require each price to be updated individually. However, if you use a product CSV, depending on the program you use to update the CSV, you may be able to create a formula to automatically update the prices to reflect the percentage change you require. If you're using Google Sheets for this, more information on creating formulas is outlined here.
While the above two options can help change product prices, they don't offer the ability to update all product prices at the same time from directly inside the Shopify admin. For a solution that offers this instead, I recommend using apps. Some integrations that provide this functionality are Bulk Product Edit & CSV Import or Bulk Editing by Booster Apps. Both of these apps are third party integrations though, so if you have any questions about using these apps, or about the billing associated with the apps, I recommend reaching out to the app developers directly for more information.
In the meantime, I understand how useful it would be to have a feature like this built into our platform, so I'm going to share this information with our developers. Our teams use this type of feedback to improve our features and services, so we really appreciate you taking the time to post about this. If our teams add a feature that allows for this in the future, we will share this update on our changelog and also on our Announcements page.
Please let me know if you have any other questions or concerns and I'll be glad to assist further!
My name is Alison, and I'm the Customer Success Specialist for Ablestar Apps. Our Bulk Editor app has this ability built in, and it also has a free version available that allows for 5 free in-app edits and 5 free spreadsheet edits a month.
The following price editing features are available in the Bulk Editor app when doing an in-app edit:
If you have questions about it feel free to reach out to us at email@example.com.