Not sure what you mean by "weren't making much from keeping them closed-access". Paywall publishers earn the bulk of their revenue from charging academic librar

Not sure what you mean by "weren't making much from keeping them closed-access". Paywall publishers earn the bulk of their revenue from charging academic libraries subscriptions to the journal content. This subscription revenue can only exist if the content is not freely available to all. So there's definitely a big pile of cash that keeping articles closed access brings in. The worry about having OA articles isn't that you might miss out on the $30 pay per view charge that you or me run into when we hit the paywall, that's almost inconsequential from a revenue standpoint. It's the worry that they won't be able to charge a library a yearly subscription fee.