You may try to use this Table Calculation:
MIN([Secondary_datasource].[Price]) * SUM([Products_sold]) / TOTAL( SUM([Products_sold]) )
You should have your blended field(s) in a view (in Details, Rows or Columns),
make sure these fields (Dimensions) to come from a Primary datasource.
The Table Calculation above is set to Compute using your blended fields.
Hope this could help.
If not, please share a sample workbook with your data and a desired output.