OK, here's the bottom line:
1) Red Hat includes support, and guaranteed updates, and you can be sure it will be continually updated in a timely manner.
2) You can call Red Hat for assistance
3) You also get content that is not included in any free distro, the Red Hat Value Added content
1) CentOS gives you a remastered version of Red Hat EL which is potentially 2 to 3 versions behind Red Hat.
2) You get the support you pay for, ie: Being told to RTFM before you're entitled to any assistance from the community. Help that's limited to what users of CentOS can give, because the developers won't waste their time helping you, even though it's Community ENTerprise OS, they really only put the distro together for themselves and don't really care about the community.
3) You can't be sure that the updates are up to date. In most cases, the updates you get are lagged significantly behind the Red Hat release, that it could leave a known security hole in your network, in a business environment this is dangerous.
Don't get me wrong, I love FOSS, and I infact use CentOS on my home server, but I also know that I have to rely on myself and those I personally know, when I need to fix something that I'm struggling with.
In a business environment, I would insist on only using a distro that has the backing and support of a company/organization that is capable and willing to support it, like Red Hat is, without saying RTFM before I'll help you. With Red Hat, you are paying for that support, and they step up to the plate to give you what you're paying for, regardless of how elementary or advanced your knowledge level is regarding the product, or the complexity level of the issue you're calling in about.
In other words, you get what you pay for, but in a business environment, you should consider if it's worth it to pay for support or get little to none.