Make or buy decision are about whether a products or services should be made within the organization or bought-in from an external supplier.
For a procurement professional to establish which method (make or buy) offers the best value, the item in question must be thought through if it is core to the organization and which option will add more value to the organization, as regards achieving its strategic goals. If it is core the procurement professional decide to make it and if it is not core the product or services can be bought in.