You can set sale prices in your flat file templates to update your listings on Amazon in bulk. You need to edit the related target fields and use the predefined source fields in the template.
Here are the steps you need to follow:
1- Go to “Settings>Templates”, find your Amazon flat file template and click edit.
2- Find related sale price fields including start-end dates and map the related fields, if not mapped already, after you have uploaded the source file when creating the flat file template.
You can check the template output for the related SKU by clicking “Template Preview” and searching the SKU.
3-Select the related products and send force price update to the channel.