A cost estimate puts a figure on what a service uses up, from your products' cost prices, so you can see what each treatment really earns. Set it once and the products keep it current.
Price is not margin
A $120.00 treatment that uses $38.00 of consumables isn't the earner it looks. The Cost estimate section of a billable service lists what the service uses up and compares the total with the price. It doesn't change what invoices charge, but when the service is invoiced, the products listed come out of stock in those amounts; a flat rate counts toward the cost only.
Open Settings, then Billable Items, open the service and go to Cost estimate
The top shows Sell price (excluding tax), Est. cost and Profit.
Under Add a product, search for each consumable the service uses
The product must exist on the Products page with a cost price and, for measured use, a unit value such as 250 ml; a product without one is flagged until you set it. Each added product shows its cost per unit.
Say how much is used
Enter a Value in the product's own unit (for example 30 ml of a 250 ml bottle), or choose Flat rate to count a fixed cost per service regardless of quantity.
Save the service
The estimate is stored with the service and recalculated whenever a product's cost price changes.
The estimate is only as good as the cost prices on your products. Update a product's Cost price when a supplier's price changes and every service using it is recalculated.