As an instructor, if you consider the students financial situation, and do the best you can to save your student money, for example: telling them what to study and read, telling them how to prepare for a flight, telling them to couch fly often. Then they will realize this and feel much better about coming to each lesson to fly with you.
Also...If its a bumpy day, and as an instructor, you think a flight today in the conditions will not help the student much, voice this to the student, and they will think very highly of you for doing so.
I have been fortunate enough to have an instructor who treats me this way, I remember sitting in a piper warrior, just about to fire the engine up, and he suggested I listen to the AWOS for a few minutes. The winds were increasing, and the ceilings were lowering, and we decided that a flight in those conditions would be a waste of money, even if we stayed in the pattern.
30 minutes later, it got pretty bad, a cold front was just passing through.
My point is, if a instructor considers the students training so important that he will suggest canceling a flight because he/she thinks it will do little to help the student, it will show, and the student will tell his/her buddies about the instructor, increased business, everyone is happy!
I am only half an instructor, almost done!