Queue Cost

A Queue node’s Cost tab has one field.

Cost Per Unit

Cost Per Unit is a flat amount added to an entity as it leaves the queue. Despite the name it is not per unit of time and not per unit of capacity: it is one charge, per entity, once, on exit. Use it for the cost of handling a piece into and out of storage, or a fixed fee for passing through a holding area.

Because waiting is waste, the charge is always counted as non-value-added. There is no value classification on a queue to change that.

Charging for time instead

If what you actually want is a cost that grows with how long an entity waits, this is the wrong field. Set a Waiting Cost per hour on the entity instead. It accrues wherever the entity waits, including in this queue, and it too is booked as non-value-added.

The two combine happily: a per-entity handling charge here, a per-hour holding charge on the entity.

Only a Queue node has it

An activity’s built-in input and output queues are not Queue nodes and carry no Cost Per Unit. To charge for a wait in front of an activity, either put a standalone Queue node there, or use the entity’s Waiting Cost.

For how this figure joins the rest, see Costs in a model and the Costs report tab.