Great thread. It is indeed a massive strain. SIs work in fostering engagement but then they became a business model and stopped working. Low cost and mass produced by new publishers marketing the APC model and exploiting publish or perish. Society owned journals have lower margins for good reason.

It says more about the incentive structure IMO. The author could publish in a different journal with a lower APC. High APC journals are (almost) always high prestige. The price would reduce if people didn't pay it.