This feature is allows you to compare the Unit Cost field for Products in the Project with the Unit Cost field in your Catalog.
This is essentially a shortcut function for the more robust Compare with Catalog feature specifically for Unit Cost.
You can manually Edit any product via the Edit button or you can use the Update from Catalog or Update to Catalog functions:
There are price options on the bottom left corner of the interface:
If you want to export out the comparison for review, you can export to either PDF or Excel: