Usually cost/benefit arguments do consider the benefits. If I kill millions of mosquitos and reduce malaria fatalties by 100 per million population while blinding 1 per million, then unless there is a
better way to kill the bugs we should consider this approach.
I don't really see how this line of argument really translates to this issue with Google. First of all I should have acknowledged that imprisoning data is almost assuredly unacceptable and that unless Google is acting directly in response to a law enforcement action they should give you a way to download your data when they tell you that they have chosen not to continue the business relationship they have with you.
But there will be cases where they cannot do that, and in some cases it will be a mistake but the reason they cannot solve this problem cheaply is because usually it is not a mistake and so litigating 99,999 cases to find the one worthy of saving is a hard case to make, why should Google pay for that?
I should have mentioned up-front that this article scared the hell out of me and I'm probably moving to Fastmail. I've had my own domain for going on two decades and am still grandfathered into the free gsuite for it but I'd much rather pay someone who will support me than use a free service that could cost me access to data that I might want again in the future. I also realized I could be vulnerable to a trap where my DNS account is disabled at the same time my email is, meaning I couldn't even move the DNS without first recovering access to my mailbox.