This might tie into mini conversions.  Selling each but assigning weighted value. Deeper than it seems.

Currently the parent 'cost' and the sub cost can be different. 

But they must share the same unit of measure, however mini conversions would allow each sub to be broken down into different UoM's 

This is mini conversions. srb

This client uses minimal parent items ie Blue Dream is the parent item for bulk, 1g shake, pre roll, 3.5, 7g. and 28 g. So 6 items. They designate the weights through sub attributes. This keeps minimal parent items and works well. Except, when they bring the items in- because they package them at one place, then bring them in. So, instead of being able to create one line item for Blue Dream with 6 subs underneath to represent the various weights, they have to bring in another line item for each weight, since the cost of each weight is different, and the cost must be identical to that of the parent.