In order to calculate unit price for the manufacturing order product, click on the Calculate Price option in the menu. 
This option will recalculate Unit price and place a new value in the Unit price field. This new value is calculated from the:
- total amount (of the manufacturing order)
- product quantity
The total amount divided by the Quantity gives you the Unit price amount.
Total cost amount is the sum of cost amount for all manufacturing order items, and cost amount for the single item is calculated from Quantity and MAC fields. For product items, MAC amount is actually MAC amount from the stock records and it can't be changed while for service items there is no MAC (because there are no stock records) so you must enter service fee/cost in the MAC field for all service items on the manufacturing order.
In some cases you may edit created documents which may affect MAC values of the approved manufacturing order. In such cases you need to refresh your stock data.
After you have recalculated new MAC values, within the manufacturing order details you may use the Update MAC option from the options menu.