Personal experience here.
My Methods SAC mark was initially fed incorrectly to VCAA, so the first time around I got a 46 in Methods with an A for SACs and A+ in both exams. However, I thought that was ludicrous as I got 98/100 for SACs at school, was ranked equal fifth and everyone on my SAC mark or 99/100 got 49s and 50s. I phoned the school and it turns out that my SAC mark WAS entered incorrectly.
In the end, my SAC score was rectified and my study score went up to 50. This means that my exam score must have been pretty awesome. However, despite an awesome exam mark, with an A for SACs, I was only able to get a 46.
Now this may be different for other subjects as Methods SACs are only worth a 1/3 of the total grade, but I think you can see the point. Even with an A for SACs, it will be extraordinarily difficult to get over 45+ as you really have to get almost 100% on the exam. With a B, a 45+ would be impossible, in Methods at least.