Hey Matthew and others,
I came across this post while researching ProcessWire and was wondering about your calculations a bit. You say same-day support comes down to $23998 per year, but in my eyes, it comes down to $3588 (The level you mention actually provides and I quote Ellislab on this: "guaranteed first response in 4 business hours")
Also, you note that the cost for a SINGLE site is $24000, which is true but you fail to mention that with ten additional sites, the platinum support would still handle your queries, at no extra cost apart from the initial $1999 per month fee.
Please note that I am in no way affiliated with Ellislab, other than being a previous customer and now looking strongly at ProcessWire, but this seems to be a lot of FUD.
Compare this to the support options of ProcessWire. Yes, it is open-source, so I can just go in and fix bugs myself (do most users really do that, though?) At the same point: ExpressionEngine code is unencrypted, so I could, in theory, fix bugs myself (I am just less likely, seeing how this is a bug they should fix, not me).
PW support here is free, but what happens if I run a client's site and something breaks and I need support right now?