Two things that can help you:
1) The mass computing of Product Costs needs to be run on an ad-hoc basic by users, but is only needed when you use the STANDARD costing method. It is not needed with FIFO or AVERAGE costing, since Odoo will automatically update product costs for you.
2) The Product Cost field as seen on the product record acts differently under FIFO. You can see the actual product cost in your Inventory Valuation report. The product cost on the product will not receive a value until you remove a unit of the product from stock and will stay at $0 until you do so. The way to think of product cost on the product record under FIFO is "the cost of the last product delivered".
Once you deliver an item you have manufactured, you will see a cost in the Product Cost field on the product record - and it will represent the cost of the last unit removed from stock.
For components, removing from stock means consume in a Manufacturing Order. You won't see a value in the Product Cost field for those products either, until they are consumed.
If this isn't working for you, review your configuration - including the valuation and costing on all of your components. I am guessing one or more of your components is setup with standard cost and has a cost price of 0.
Standard Cost in Odoo means "Odoo is no longer being asked to maintain this field - the user will do that and make sure all values are non-zero".