Tooling cost is the cost of creating the mold, jig or other one time setup cost associated with starting production. The part cost is the cost incurred each time a part is manufactured. Cost always matters when choosing a manufacturing technology.
Depending on the part molding process, the price to create a quality tool can be extremely high. For example, creating a steel tool for injection molding processes may cost several hundreds of thousands of dollars. The larger and more complex the part is, the higher the cost of tooling will be. While a lower individual part production cost may help offset the cost of a highly expensive tool for parts that are produced in extremely large quantities, this isn’t the case for parts that have lower production volumes.