BB,
The other way to look at it is that a (very low paid) instructor who only gets paid for actual flying time (in general), and has given may hours in unpaid briefings, before and after each flight, is recouping some remuneration for his/her "total" efforts in enabling you to reach your goal.
Looked at it from that perspective, and realising how much "advice" has been given when you near the end of the course, I think you will not begrude paying a dual rate (not that I am implying that is the case).
And no I am not an instructor.