With respect to students as economizing, that is maximizing, agents  
when buying text books. 
 
All maximization takes place in knowledge constraints.  The student,  
by definition, does not know what is in the book, or whether [their]  
interest and motivation will persist though the course.  The fact that  
they buy the book is not an indication of established preferences, or  
whether they will read it; and even if they do read it, whether they  
will comprehend the contents.  Indeed, some will read and  
comprehend, and get a good mark, and regret for the rest of their  
lives that they bought the book and took the course. 
 
Robin Neill