John Baez draws the world’s attention to the Banff protocol, a specific guideline for which journals to boycott for overcharging for subscriptions. You can submit your name there as a public supporter of the Banff Protocol.
I’ve seen two main arguments on the question of expensive journals: the “idealist” view, and the “realist” view. The idealist point of view is that in the Internet age, scientific information should be either free or low cost. The realist point of view is that journals are expensive to produce and no one has successfully produced a free one. This is one of those (rare? common?) instances of where the idealist view is closer to a pragmatic answer than the realist view. The actual question of how expensive journals should be is a red herring from the real issue: From a purely economic point of view, where the does the value of a prestigious journal come from? It’s not from the authors, most of whom need the prestigious journal a lot more than the journal needs them. Even though prestigious journals require prestigious editors, prestigious editors like editing prestigious journals, so it’s not the editors in a vacuum. As the idealists like to point out, typesetting is now done by the authors themselves. I’m sure copyediting and publishing a journal, and shipping it to every university library in the world is not cheap, but I’m sure it’s not difficult to pay someone to do them for you.
From the economic point of view, prestigious journals are like colas: the importance is in the brand. Acta Mathematica is not essentially different from Coca-Cola. Authors, peer reviewers, and editors all essentially donate their time (I assume that editors are paid, but not much) to contribute to the value of this brand. When mathematicians allowed ownership of these brands to pass into the hands of the publishers, they were suckers. Rubes. Marks who got scammed. They let the one thing of irreplaceable value to get away. So maybe the realists are right that publishing a journal is intrinsically expensive. But the real issue is not the price of journals, but that mathematicians allowed a system to evolve where there own career self-interest forces them to help big companies make fat profits off their work, and they did so by letting ownership of their own journals to slip away.