I missed this Steven Harnad piece from last May. It is trademark Harnad:
So, you should ask, with online publishing costs near zero, and quality control provided gratis by peer reviewers, what could possibly explain, let alone justify, levying a fee on S&S [scientists and scholars] authors trying to publish their give-away articles to report their give-away findings? The answer is not as complicated as you may be imagining, but the answer is shocking: the culprits are not the publishers but the S&S authors, their institutions and their funders! The publishers are just businessmen trying to make a buck. […] Under mounting ‘open access’ pressure from S&S authors, institutional libraries, research funders and activists, the publishers made the obvious business decision: ‘You want open access for all users? Let the authors, their institutions or their research funders pay us for publication in advance, and you’ve got it!’
Harnad, the original (and wittiest) advocate for the “green” repository route, is basically right. It’s not just scholars, of course—we’re not free agents when it comes, say, to productivity metrics imposed by university managers. But the academic system as a whole (funders included) is responsible for letting the oligopolist publishers laugh, as Harnad has it, all the way to the bank.