Multiply each entry prior to Sum

I have a Table that lists Engine parts that roll up to the Engine number.  

So my table only lists the engine numbers and you can drill down to see the parts.  

My hope is that I can get a cost per lb for each motor from the table.  It would have to multiply the individual qty times the cost per lb.  Instead the table is multiplying the sum of quanity and sum of total cost per lb.   I would like for it to do the calculation at the dropdown level and then sum.