This should give you a good starting point. Product Extensions can be downloaded as a XLS file and handled this way. Of course, this procedure can be automated but then it is best to check with your PFX project team how to do that.
You can also use the Data Source templates.
This way you can create a Data Source based on existing Product Extension, Customer Extension or Price Parameter table. Later you can map product master and customer master data in the connected Datamart.
This is the quickest way to upload historical cost or price list information to Data Source, Datamart and create a chart, dashboard on the top of your historical data.