@a-mblanchard @Anonymous 

NO, not really. You can change the cost price but the data is only for creating Vendor Purchase Orders.

Actual FIFO cost counts when you buy products and enter it under Vendor Item details tab either as a Bill or Check or Expense form.  That,s all you need to do. QBO will take care of the COGS side when you can create a Sales form (invoice or sales receipt).