It's not really vastly higher. If you're planning for any ATAR up to around 98 then providied you do well you will be able to achieve it. Mathematics does scale better, and allows you to go on to get a 99+ atar easier(without getting state rank). Scaling wise Mathematics does better, but in terms of RAW marks there's only around a 5-6 mark difference for a band 6 in either subject.
Financial Services is in it's first year as a subject so there's no data to tell whether it is or not. But because it replaced Accounting we can go off the data from that, which suggests the subject is fairly decent in terms of scaling, it's sort of inbetween say...Physics and Studies of Religion , leaning closer to Physics. Because the course is in it's first year though,the cohort this year might be slightly worse or better. Given my current cohort for the subject it seems the subject will stay in scaling,plus looking from the only trial paper available, it's going to be a fairly easy test.(especially with the test counting 100% to our HSC mark)
