Replacing CentOS/Scientific Linux with Red Hat, the politics not the technical

This one may be a touchy subject on the Red Hat discussion pages but I am interested to know people's thoughts and approaches to the following.

You are an administrator / system engineer in a medium/large environment that is running a CentOS/Scientific Linux as their chosen Linux distribution. What 'sales pitch' do you give them to convince them that the expense of Red Hat licenses is worth the outlay?.

I have personally been in this situation and managed to convince one customer with the argument of central management with Satellite and corporate support for vendor supplied applications. Now though, Spacewalk is available for CentOS users and with Red Hat putting their weight behind the CentOS project it almost legitimises the argument to stay with CentOS to a CIO trying to save money. I am also finding vendors that are happy to support deployments of their application on CentOS, so the argument gets that little bit more difficult.

Without "call in the Red Hat sales team", how would you approach the subject with the decision makers in an organisation you are responsible for?
Have you been through the process as well?
What were your experiences?