C.o.g On Products And Add On Products

Can there please be a way to add in a SKU for Optional add on's to packages/collections.   

I can add the cost price of a product base  (print) and have it come up on the product export report as an SKU  - but I cannot add in a cost for any optional add on's that customers can add to a collection/package/ buy all eg extra photos. 

All it would require (if this is possible ) is to add the Reference Name / ID in the pop up box when creating an option to a package.  Just that extra field. 

This would make adding up the COG for each job so much easier if this was to be added other than manually having to add in print costs for the additional items. 

Please and thank you.