ROI and educating the client

In a lot of the industries that our PR firm works with, it is difficult for me to really detect the direct benefit that PR has for their business, due to the middle man coming between the media coverage and the company making sales. For example, if a medical technology company makes a device, they are not generally the focus of the media coverage. Sometimes, the users do not even find occasion during the interview to mention the name of the actual company. So does this increase sales for the client? What is a good way to measure something like that?

This article really intrigues me because a lot of time in PR, people don't take the time to really think about the significance of one clip v. another. It's not just the more you get, the better. It is quality over quantity in my book. Targeting v. mass attack. Strategy should come into play. All important things to remember.