You are using Invoicing > Find Documents > Sales Invoices to determine the subtotal of the items for a sales invoice and also the Commissionable Cost, which is a User-defined Cost.
Looking at certain sales invoices, they are displaying an incorrect amount for the Commissionable Cost (CC). In the browser that opens, the CC is different than the document's actual cost. Nothing else under Pricing Analysis shows the CC value.
You are using Everest version 6.
This behavior is a known defect affecting Everest version 6, caused by the Inventory Costing using the same value as the User-defined Cost directly, instead of splitting to a different account. This approach may create a negative balance of the inventory valuation.
In the latest release, the behavior is indeed showing a single entry of Cost of Goods Sold with an entry type of Cost of Goods Sold (commissionable):
To overcome the issue, please upgrade to the latest version, and make sure that the Type of cost used for commission calculation is set to User Defined: