How to write to power BI DASHBOARD

To achieve the same requirement, what you can do is to create a Power Apps [Canvas App] from Power BI Desktop which you can find in the visualization pane, and you need to manually create the application which fulfils this requirement.
Instead of Enter Data you can use SharePoint list as data source, refer that list as data source in Power Apps and provide a basic UPDATE functionality in the application.
As soon as he updates the value in the Power Apps Visual in Power BI, the sharepoint list value gets updated and then the value in the table visual in Power BI will also be updated & the measure you created will automatically compute the fresh value based upon the Updated "New Price" value.

This is somewhat a reliable link pertaining to the same topic.
https://youtu.be/NTUfX9HNdK0 

Thank you. 
Let me know if you have any query regarding the same.