The book business is very different from what it was years ago. Small press runs can be cheaper than large ones. The reason is that some states tax inventory by wholesale value, so having a warehouse of $50 books is much more expensive than having a warehouse full of blank paper and a few boxes of color covers.
The publisher can do a short press run to meet the pre-orders from the large bookstore chains and direct order, get some cash flow and be ready for another short run, based on actual sales figures. My grandfather owned a print shop and ran a Linotype (Google it); a book was a lot of trays of lead type that had to be stored. It was cheaper to store printed books than to keep the type around. A minor change was a very physical operation, and a major change was awful.
Today, a book is in digital media and the modern version of a printing press sets the type directly from it. You load the ink, the glue and the covers into it. The machine does the printing and bindery, and spits completed books out the back end.
But this also means that minor typos can be fixed between printings as easily as changing a word processing document. All that most publishers want is that the pagination stays the same from printing to printing. This will let them keep the same index, which is important for searching.