Field help (ITMREFPJM1) 

Saleable items are used by the Project management sales automation functionality to generate the list of saleable products on a project (called from the project budget level or the project task level).

The service item you define in this field will be included in the list of saleable products on a project, if this cost type is defined on a project budget line for a chargeable budget code, or to a resource planned for an operational task. Sales documents will be linked to the operational task code.