Reprint houses

The Joan Murray and Rosalie Moore books were both reprinted by AMS Press in 1971.

Which makes me wonder if there are any operational or business model records for AMS Press, Arno, Books For Libraries and other such reprint houses from decades ago. Clearly none of them were profitable enough to stay in business until today, but I;m curious how they were able to stay afloat at all and if ther'es anything that could be gleaned from they way they did business then that would be instructive for us today.