The reference to Amy Hoy's Charm is interesting, just because that was such an interesting (and somewhat distressing scenario, if you're into RoR and Ubuntu).

But to say that the Windows architecture is significantly better bang for the buck requires more of an apples to apples comparison. The best I can find is that Hoy describes Charm as having 3,800 interested users in Oct. 2012...The OP describes having hundreds of companies (each with a variable number of users) issuing about 1,500 support tickets daily.

(I'm not counting the traffic visits to the blog because that should be trivial, in the scheme of things, to manage...though I guess kudos for putting it on the same server as the software platform?)

I guess knowing the other costs, such as developer time/salaries, would be helpful.