Building relationships in data model to leverage power pivot - circumventing unique key ID issue

Thank you for this I'll start learning some DAX and this virtual relationship connection.

I am finding though that using that formula adds that total COGS amount ($7,500) to each Service Line row of the sales table with the same productID, and then sums it up, so I'm actually getting an aggregate of the aggregate now ($7,500 * 5 = $37,500).  Is there something wrong with my formula?  (couldn't find 'TREATAS' so used 'INTERSECT')

CALCULATE(SUM(COGS[COGS]),

INTERSECT(

                  ALL(Sales[Service Line]),

                  VALUES(COGS[Service Line])

                  )

)

I think it may have to do with the fact the sum has to be on 2 categories / criteria (Product ID and Service Line), whereas right now it's aggregating the total COGS per ProductID, and adding that to each service line (and then summing that up).