@99.9% sucks
What? Nine hours a year is complete crap? I'd love to see how you justify that, even with your "weighted average basis" of course (whatever that means). Even assuming your weighted average basis means the CEO gets all nine hours of downtime at once, I suspect you'd be hard pressed to make a case that it caused anything other than inconvenience.
But the real question isn't one of absolutes. Say Google only gets 99.9%, or 99.7, or 99.99. How does that compare to what the alternatives are? No service is perfect, even ones administered internally. Perhaps *especially* ones administered internally, if you're a small company.
So, figure out if your favorite other service is better. If it is, figure out by how many hours better it is, divide that by it's cost, and compare that to your potential lost revenue from down time. If it's cheaper to just suffer through a bit of down time, guess which way companies will go? And if it's cheaper to pay to not suffer the downtime, guess which way they'll go?