Looking at homework 4, there is less than complete clarity in distinguishing “Resources”, “Unit costs” and “Cost”:
Resources: The inputs required to deliver the service such as personnel time, supplies and equipment. These are the things themselves, not their dollar value. Sometimes resources are called “ingredients.”
Unit cost: As the term suggests, it's the cost of a unit of the input, such as hourly compensation for personnel, or the cost of a 10mL syringe, or the cost of a dose of an antibiotic.
Cost: This word is used different ways in different contexts, but for our purposes here, it is the number of units of a resource x the unit cost of that resource. If you sum that product over all of the resources required to deliver the intervention, you have the total cost of that intervention. This method is often referred to as "Ingredients-based" costing or "Micro costing".