The communication infrastructure of modern science is provided by profit-oriented business firms: the publishing houses which print and distribute academic books and journals. Surprisingly, beyond some rather superficial impressions, in science studies little is known about how academic publishers work--in particular, how markets for books and journals look like, how publication decisions are taken, and how the interplay with the scientific community is arranged. We address these questions with a focus on the relation between economic considerations of publishers, on the one hand, and the requirements of scientific communication, on the other. Our contrasting case studies are a very large worldwide operating publisher with regard to chemistry publications and a national publishing house of German sociology. At first, we show how the rather different business approaches of the two types of academic publishing houses look like. Both approaches could reach stability for some time which means not only that publishers earned money according to their profit aspirations but also that the communication requirements of science were sufficiently met. Afterwards, we point out the instabilities that have begun to arise in both fields and may sooner or later erode the former fit of profit-making and scientific communication.