Point 1: Traditional journals are overpriced by an order of magnitude.
Overall, publishers earn about 3800-5000 euros per article they publish. The true costs of organizing peer review are much lower: a few hundred euros per article at SciPost or PeerJ. The difference is therefore not mainly due to commercial publishers’ profits, but rather to large inefficiencies at all traditional publishers. (Have a look at the salaries of the American Chemical Society’s executives.)
Some publishers also use the money for subsidizing other activities, such as conferences (learned socities) or science journalism (Nature, Science). While these activities are valuable, they are not the main purpose of scientific publishing, and should not determine its future.