Your salary was the exact kind of thing that needs to be balanced against the cost of fraud; if it was larger than the amount of fraud you prevented, then the company would have been better off just accepting the fraud as a cost of doing business. The closer you get to zero fraud, the more expensive it becomes to reduce it further (and the more likely your countermeasures will negatively impact the business in other ways), so there definitely is an "optimal" balance to be struck between fraud and preventive measures.
Your salary was the exact kind of thing that needs to be balanced against the cost of fraud; if it was larger than the amount of fraud you prevented, then the company would have been better off just accepting the fraud as a cost of doing business. The closer you get to zero fraud, the more expensive it becomes to reduce it further (and the more likely your countermeasures will negatively impact the business in other ways), so there definitely is an "optimal" balance to be struck between fraud and preventive measures.