Well, two things here.
First: Really, the requirement for vendor 'support' is something I've always had a bit of a hard time rationalizing.. Getting a vendor in for consultancy/implementation help is a bit of a different story though and is often worth it.
Back to support.. The old "Alright, we pay RedHat or Oracle for support for when something breaks" thing.. The reality is when something does go arse over bollocks you'll get two options from your vendor (at least from sun, oracle, redhat, ibm and sap in my experience): upgrade to the latest version, or downgrade until you get a code fix from the vendor. Your critical oracle 10 db running on some older redhat point release shits itself? Not their problem. Hope you have backups. They will take file a bug internally to prevent it happening again but they can't do much more than you can internally to get things back up.
I've been in ops for almost 15 years and I still don't have a single story of a vendor 'saving the day' outside of hardware support (actually, that's not true -- once Joyent solved a problem for us by patching some servers within about an hour of us reporting a problem which remains the single greatest support experience in my life).
We worked out how to do software upgrades and rollbacks a decade ago, if one shitty linux kernel package is enough to down your business then yeah, you're doing things wrong and hopefully will learn from the experience, but paying a support fee per instance isn't going to help you recover or avoid those things.
I think we agree, all I'm trying to say is at least in my experience: You're almost always better spending your money on good staff than support contracts.
Second: In what world do you live in that your sysadmins can write kernel patches during prod outages? Maybe your reality is very different to mine, but adding/changing code has never been the solution to bad outages (and I've been through some gnarly ones, trust me) for me so far...