Earlier quoted context omitted.
The thing RedHat sells isn't the OS itself.
This is a little bit off-topic but... they removed basic support and now there's a "self-support subscription" option instead for $350. If you don't get support for that subscription, I can't see a difference worth $350 between RHEL self-support subscription and CentOS. EDIT: ate a word EDIT 2: self-support desktop subscription is just $49. But the point is the same: no support.
* Access to the RHEL repositories, with faster updates than CentOS or alternatives.
* Ability to upgrade to supported tier.
* Possibly: access to RHN pages with their forums, documentation, etc?
None of which would be huge advantages to me, but I can totally see the potential value.