Defining profit value in usability testing

Question: Is there a method of defining potential profit value or loss on visual design tests?

Background: I was recently asked how to quantify a profit value or loss based on a set of tests for improving readability on a website. I had set up a few sets of 5 second and first-click tests. After each test I asked three open ended questions regarding why they made the choices they did and a finished with a 1 to 10 rating. I have been looking for a potential value equation or someone who had come up with a method to define value for visual tests, but have come up short.