I’m looking at how to configure a base that will allow tracking of made products (in this case jewelry) along with the stock parts that make up each item. I then need to have it calculate the cost of all the stock used.
The jewelry table should allow allocating/picking the used stock items and ideally then total up the cost for the units of stock used.
The stock table should calculate remaining stock.
I’ve read this page on One to Many and Many-to-many relationships and junction tables:

A beginner's guide to many-to-many relationships
What sets Airtable apart from ordinary spreadsheet applications is its ability to link related concepts together. Knowing how to represent the relationships between different groups of objects can ...
I think I have a one to many relationship however the complexity of trying to total up the cost meant I tried a third table called ‘stock used’ but it means manually entering the jewelry item multiple times and then separately allocating the stock item against it. Which doesn’t seem very elegant. See images below:
I’m wondering if this is the best approach, if it could be refined or if there are any suggestions on how to tackle this?
Thanks