I have a requirement to record product cost in the orders_products table. I have the cost of products without attributes figured out, and cost of products where only one value of an attribute can be selected figured out. But now I have a new requirement where multiple values of an attribute can be selected, and can't quite figure out how and where to calculate the product cost.

A hypothetical example might be purchasing a computer with pre-installed software. The attribute (option name) is "Installed Software" and the attribute values (option values) are (1) MS Office, (2) Chrome Browser, (3) Adobe Reader, (4) Auto CAD, and (5) Photoshop. The customer can select one or more packages for the seller to install and ship the completed computer to the customer. The cost of each software package differs of course, so the total product cost would be the sum of the bare computer plus cost of all software packages installed.

So can someone please suggest an appropriate notifier to use with an observer to calculate the total product cost in this scenario? I'm currently using NOTIFY_ORDER_DURING_CREATE_ADDED_ATTRIBUTE_LINE_ITEM but I suspect there's a better notifier to use.

I have Stock by Attribute installed.

Thank you for any suggestions.