Some vendors provide commercial licenses of Linux, including support. What is the real benefit of these? Is it worth the money?
Considering the incredible amount of information and support available on the net, and considering that Ubuntu server is available for free (for example), why should one spend money on RHEL (for example)? What is the added value?
Shouldn't one spend money on a good system administrator instead of a commercial version of Linux? What is the tradeoff? Is it worth it?
Buying a commercially supported version of Linux does not absolve you from the duty of hiring good sysadmins. The way you stated your question, you seem to think that any monkey can run RHEL (for instance), but I can assure you that is not the case. Either way you need good sysadmins.
The difference is that if you pay for RHEL, there's someone on the other end of the phone to help take care of some things when they go wrong. There's also a team at RH that's proactively finding out about security and patching issues and keeping your sysadmin up to date (so that your sysadmin doesn't have to spend 3/4 of his or her time keeping up with Bugtraq and hunting down the latest patched packages).
This gives your sysadmin a little more backup and in theory lets your sysadmin accomplish more locally. It doesn't let you fire your good (highly paid) sysadmin and replace them with a grad student with a Cheetos fixation.
IMHO, you are wasting the 10K Red Hat contract if you don't have a good sysadmin. A good sysadmin will do much much more than just troubleshoot problems. Disclaimer: I am a sysamdin :D
Your first step should be finding a good sysadmin, and then talk to him about whether or not you need a RHEL contract.
If you're still at the point where $10k/a can affect the quality of the sysadmin you get then you're not likely to be ready for a RHEL subscription regardless.
Large, serious corporations don't need to look at $10k to get the best person for the job. Small corporations need a decent sysadmin more than they need the vendor support.
It's a matter of scope; distros are designed to do everything for everybody. A sysadmin makes that one box do that one job that it supposed to do. Even the greatest tech support is not going to be aware of your political/regulatory/human/situational constraints. They're not gonna be aware of all the other boxes out there that this box must talk to.
Distros are a starting point, a building kit. A sysadmin is the only one that can take the packages and frameworks available in the distro and make it into a coherent setup that ultimately turns a server into a non-problematic member of the larger system/network.
There is one case in which 'vanilla' distro will do a fine job: anything trivial, requiring no configuration/customization, but if that's the case, you'd probably be better off buying a service then, so someone else can worry about the infrastructure (ie. backups, power, network plumbing, etc).
I'm not sure what the support contract entails, but usually when you buy support, it's to guarantee fixes and repairs on your installation. A good sysadmin is keeping your systems running day by day and doing a lot of additional tasks that the support contract doesn't cover.
Then there are times where you're expecting one person to know DNS, DHCP, client configs, backups, email, RAID, driver issues, etc. etc. etc. and sometimes there's a slight chance that he or she will bump into something he or she isn't familiar with. It happens.
So that's where your support contract comes in. If you have a critical system that cannot go down, your contract means that your admin has access to people that know the internals of that distro and should, in theory, be able to help him or her get through a rough patch or get preferred support. On the Internet there is help available...but it may be outdated, it will definitely not be obligated, and it may be inaccurate. The vendor is someone who can be held accountable and is obligated to assist since you have a contract, and Googling through support forums and help sites when you need that web server back online NOW is not very efficient.
It comes down to your support needs and how much your uptime and system availability is worth to you. The contract may pay for itself in the first emergency you have, rather than pinning every bit of responsibility on a probably overworked and overstressed sysadmin.
I think of myself as a good sysadmin :) I actually use CentOS and Scientific Linux in many installations, keeping a token RHEL license every so often. I've rarely needed to call Red Hat for support (thrice in 8 years), but it was handy in order to confirm an odd compatibility or fringe issue.
The other factor may be vendor support. Perhaps you have an application that requires RHEL as a target platform. Maybe there's a hardware component (server or peripheral) that is only certified for Red Hat or SuSE. That's typically where the commercial distribution is important. When I've encountered those cases, however, CentOS was 99.9% of the way there. It's a good stand-in.
The most recent issue I had was needing to purchase Red Hat MRG for realtime kernel support. Since Scientific Linux now provides a proper recompile of the MRG source, I have very little use for the commercial product in my environment.