As Sourceninja was saying, Redhat is not targeting home users with an $800 system. They are selling this to massive data centers where $20K in licensing is a drop in the bucket.
Redhat not only supports but certifies their enterprise Linux for application compatibility. I'm not sure if it's changed but the only Linux Oracle offered support for was Redhat. IMHO, Redhat has played very nice within the Linux community by contributing a ton of code. A couple times they have sic'd the lawyers on some re-packaging of their enterprise stuff but that was only to have their trademarks removed (for which I don't blame them). Think about that -- can you imagine Microsoft ever saying, "Sure, you can make free copies of Windows 2003 Server as long as you remove our logos"?
That's the wonderful thing about Linux -- it covers the spectrum from tiny, single PCB systems to huge clusters to supercomputers. For folks like us, there are plenty of free distributions.