When you sync estimates with QuickBooks, you will notice that when you view the list of estimate line items in the estimate entry screen, the cost per unit is blank, but when you view (or print) the estimate formatted for printing, the cost per unit always equals the item total. 

For example, say an estimate item in ContractorTools has a quantity of 4, and cost per unit of $5.00, for a total of $20. When you view the estimate in the estimate entry screen, this line item will have quantity of 4, and a total of $20, and the cost per unit will be blank. But, when you preview or print the estimate, the cost per unit will be $20 - same as the item total. 

When ContractorTools writes line items to estimates in QuickBooks, it writes the quantity and the total, but not the cost per unit. QuickBooks is supposed to either back into the cost per unit by dividing the total by the quantity, or leave it blank. But it doesn't do that; it plugs the total into the cost per unit. 

We reported this to QuickBooks a long time ago, but it has not been fixed.

The reason ContractorTools does not write the cost per unit to QuickBooks is related to the calculation of markups. Simply put, because of possible rounding discrepancies in calculating markups, sometimes a line item total does not exactly equal the quantity times the cost per unit.