Rate (How much do you charge per unit) is what the customer pays and is used on proposals, templates and online orders. Cost (How much does it cost you per unit) is your internal expense and is never shown to customers; for Labor items it feeds the proposal's cost breakdown, where the total labor cost is spread evenly across the meals served (by quantity) to estimate your margin per meal — Equipment cost is reported separately in the breakdown since it doesn't scale per meal. The list page shows Profit margin as rate minus cost per unit. Changing the rate later does not update lines already added to existing proposals — each proposal line stores the rate that was in effect when it was added, and you can still edit that stored rate inline on the proposal.