Quantifying value add by a PM

I was discussing the issue of value addition with my delivery manager. My point was while someone is managing a project, his / her main objective is to successfully complete the project with the minimum amount of issues. So at the end of the day, if one asks the PM, what is the value you have added to the project, the PM can say that I did this and I did that to mitigate this or that risk, I handled this situation in this way and finally the project was completed with minimum issues. But then, can the same be quantified? To this, my delivery manager asked me, what the biggest risk in any project is. As per him, the biggest risk is in loosing the customer, loosing the revenue stream that is established. So if you do anything that will keep the revenue stream intact and keep growing it, that is the value add. Everyone’s contribution may or may not be measurable in dollar terms. Sometimes, what the client pays can be considered to be a measure of the value add; but them it is a great leveler. The client doesnot pay as per individual ability or value add. It is a negotiated amount for a minimum general set of abilities. Even if you do a value add, the client doesnot pay you extra. So, it is very difficult to put a dollar value to it. I agreed to it. Also, another point is that the client appreciates someone when that person really contributes. And though a PM may be handling a team, he can many times act as an individual contributor and add value. Also, in the overall sense, if the team delivers the project successfully, the PM gets his / her share of appreciation. However, this cannot again be quantified. May be some one should come up with a frame work for the value add done by a PM.