In any item assembly there will typically be a labor and a material item that make up the final per unit price. The labor price will be an important roll in what the final price is per unit in the assembly. To edit your labor price navigate to Settings > Item List.
Click the Labor box to show just the labor items and search for the specific labor item that needs to be edited.
Click the Edit button next to the material item that needs to be modified and choose edit item. In the edit item dialogue change any aspect of the material you need to except the type. In this example interior wall paint will be $45 per gallon in any estimate this item is added. Save your changes before exiting this screen.
Changes to the material price will also change the unit price for any assembly.