As economics is a not so common subject im curious to know how it will scale as such with my sac grades - I have done 5 sacs over the course of unit 3 averaging only 74%. If i maintain this grade for unit 4 (it is my worst subject by far) and achieve a similar result on the exam, what kind of study score could i expect?
74% on everything would give you low to mid 30's. Keep in mind eco usually scales by around 1.5-2 study scores so that can boost up the result a bit.
Economics is still quite a popular subject and unless you have a very small class SAC scaling is the same as other subjects.
A common mistake students make with eco is rote learning. Eco is not a rote learnt subject, it needs time to understand the concepts and now how they relate to each other and how to apply that knowledge. (just for some general advice).