There must of been more to it than just not checking your mirrors, but yeah they are very strong on you checking your mirrors all the time, just remember ALWAYS check your mirrors before braking and indicating.
Driving instructors arent usually worried so much about how much money they make, but your saftey and the other people around you on the road, and if they feel that your not safe enough for the roads, their going to fail you. Just imagine if he passes you when hes not confident in you and you go and have a crash and get seriously hurt then it reflects on them.
Anyway enough of the lecture, i paid $200 to do my test, it was $100 for a leeson before my test and then another $100 to do the test, if you feel you dont need to do the lesson before the test, thats $100 you save.