A reasonable request is not to shut all prestigious publishing monopolies down, but to ask/beg/fight them to be less greedy. As you mentioned, publishers run market places and sell distribution channels. They do not need that high margins to run the business. Where the profit goes to? Not the science community, but heir owners and executives high up on the rank who do not contribute much but get the most cash rewards. I believe this is what worth fighting for.
I would go even further and say that these prestigious institutions don't need any execs. They are just a pressure tool for corporate interests. There's no shutting down needed, just dismantling their bureaucracy. If there is one community where self-organizing is genre consensually known to work it's the academic community. There are already tons of fields where this is the case: some top-notch-international and most local conferences and journals alike in CS and math are already being run collegially by universities and unions. As always it's always where there are big corps that thing go awry (looking at you biology and medicine).
