Product Price Bulk Editing
Login to your WordPress Dashboard
Go to the Products admin page.
Click Screen Options (top right)
Set Number of items per page to display all Products you want to edit.
Close Screen Options drop-down.
Filter by Category to only edit Products in specific Category
Click the Check Box at the top of the left column in the Products List to select all Products listed or check only those you wish to edit.
Click on Bulk Actions > Edit > Apply.
Click Price drop-down.
Select Sale > Change to:
Choose Set to regular price increase/decreased by fixed amount or %”
Enter e.g. 30%