Most linux distros offer free downloads, if you want CDs you can burn them yourself or purchase the install package.
Redhat offers users the ability to have access to all of the newest patches and updates in the style of how windows performs it. Fedora is anotehr version of Redhat, it is the development/beta version. Everything is free on it. Redhat offers a support program
for business version of their OS.
The point, however you look at it though, is that no matter what, linux itself is free. Free as in Free speech as well as free as in free beer. Distro companies may charge for their contributions to the software and the support they offer, but the linux kernel
is up for use by anyone. The source is out there for you to download and modify to suit your own needs. Royalty free.