You've gone the completely other way: you're saying the service not being offered is evidence that it is cheap. This is the opposite of the typical argument. So I'm reducing your idea here to its simplest logical form, trying to make it super clear to readers (and hopefully you) how ass-backwards it is.
The Linode comparison doesn't hold at all. Linode have actual numbers to support their position. They are in a position to estimate the support costs, because they have other services they already have to support. Moreover, their product costs money and people expect that when they pay for something there will be support.
Google offers support for exactly one product (adwords). They have no basis for estimating the cost of support for a product like Google Groups. The argument that it will be expensive that you and others are putting forth is "Golly, support sure is expensive! You have to hire people and everything!" There's certainly reasons to expect that offering support might be expensive. But my entire point, which you seem intent on missing, is that they have been successful so far without offering any support at all, so why is it reasonable to expect that the demand for it will be so excessive that it would be financially untenable? Especially when people like the OP have suggested they would happily pay for it?
The other prong of your argument is that if it were tenable they would be doing it. I would argue that companies make good and bad decisions all the time. Looking to what they are currently doing with the assumption that it is the only right thing is a bit myopic. Companies miss opportunities and make mistakes all the time. That they're not doing it now is not evidence that it would be a mistake.
Since this a bald-faced lie, my unpleasantness is clearly warranted. You are clearly deriving arguments from a predetermined conclusion likely reached ages ago. At this point you apparently are trying to make inferences about demand without even trying to understand the existing supply, and the contortions you're going through to justify your existing beliefs are astonishing.
Being pleasant and gentle to everyone is not the most important part of discourse, not even on HN.
As to the accusation of ad hominem: every single point I made was directed at - and based solely on - the arguments made by the other user. Once these arguments were ultimately found to be made in bad faith, I ended the discussion. That's not an ad hominem argument, that's ending an argument because of a negative evaluation of the other person's state of mind. Two very different things - almost unrelated, honestly.
Which I don't necessarily agree with, but I think the point is worth considering and not "ass-backwards" or completely illogical.