Textbook development: 5 Tips for controlling length

You might be informed by your copy editor that your textbook manuscript is too long. Say, for example, your copy editor has returned five of your chapters marked as seriously over length. Instructions say to reduce length by the equivalent of three manuscript pages per chapter. Reading over the manuscript, barring a word here or there, you believe there is simply no way you can cut without destroying the brilliance and integrity of your exposition. You ask if the book can just be made sixteen pages longer. The answer, categorically, is no, because of the cost. What should you do?