What's preventing someone from freeloading? It sounds like regardless of whether you're paying, you can still get the patches.
It's much harder for freeloaders to accept feature requests from customers, for example, because that would result in a fork.
What's the joke where someone fixes some machine and charges $1000? Their cost breakdown was:
turning a knob: $1
knowing which knob to turn: $999
If you catch any bugs specific to your systems or need special feature Red Hat is always there to help because a lot of open source software developers are as well Red Hat employees.
If you use CentOS or whatever other RHEL-based distribution there is no support at all other the one community might provide.