The Chief Audit Executive (CAE) would be justified in reporting the situation to the organization's board if, in the opinion of the CAE, the level of residual risk assumed by senior management is too high (1). Even though the new process of obtaining written approval by the vice president of sales addresses the issue, if the CAE believes that the residual risk remains too high, it is their duty to report it to the board. The cost of implementing a preventive control or the compliance with the new process does not change the responsibility of the CAE to report significant residual risks to the board.
Reference:
The Institute of Internal Auditors (IIA) Standard 2600 - Communicating the Acceptance of Risks: "When the chief audit executive believes that senior management has accepted a level of residual risk that may be unacceptable to the organization, the chief audit executive must discuss the matter with senior management. If the decision regarding residual risk is not resolved, the chief audit executive must report the matter to the board for resolution." IIA Practice Guide on "Communicating Risk Acceptance to the Board"