Need the cost of good to be updated on ledge after submitting the sales invoice

Hello All,
Thanks for checking this topic. When I introduced erpnext to one of my friends who has a restaurant, he got this issue. He added 2 raw materials and one produced item. Then he added a bill of materials with those two raw materials (Rice, Carrot) for the produced item (Fried Rice).
However, everything was great.

But the issue he got was, after submitting the sales invoice for the produced item, he sees the total cost on the cost of goods(ledger). (If fried rice is 300, raw materials cost 150), that should be different right?

Is this my fault or have I missed something?