You don't really have to worry about the maths in economics for the hsc, but most uni economics courses have 3 unit maths as assumed knowledge. I would say personally speaking that it is quite a bit of content, especially topic 1 of the HSC course which is basically content, content and more content so in a way similar to business studies for topic 1. However overall the course does have a fair few concepts, and you shouldn't be to worried about the level of maths as long as you are a logical thinker.
In my class, only myself another girl do general maths, whilst the rest of the class is doing 2/3 unit. This was overwhelming for me at the start of yr 11, however as it turned out i am ranked 3rd and the girl is ranked 4th so that proves you don't have to be boss at maths to go well in HSC economics, uni would be a different story.