Hello,

By updating the item cost it will not change the existing records, when you will create new orders then it will take that updated cost so for now you can update the valuation records from backend to see the changes.

Hi Kevin, 
​If you haven't sorted this yet, I just had a similar issue (using v17). I was able to unlock the BoM, change the component quantity used to zero in all affected MO's. Then add the component required again to the BoM. This removed all trace of the stock moves with the wrong price and added new moves with correct price. 
Doing it this way was necessary for us as it also corrected the AVCO pricing. 

@Lars, 

I was not able to find the "Landed Costs" section where you said it was located. Is there another location that I can find it? 

You can modify cost from Inventory->Operations->Landed Cost