What kind of courses/fields are you aiming for after high school? The most important thing to think about is prerequisites. Chemistry is a prereq (or at least highly recommended) for a lot of science / health science courses, so if you're thinking of doing that after high school then you probably would not want to drop chem. VCE Economics is not a prerequisite for any course (that I know of).
I didn't do economics in VCE, but I'm majoring in it at university and the content you learn in first year is basically repeat of VCE Economics 3/4 with some extra content sprinkled in. On the other hand most of VCE chem is treated as assumed knowledge in uni (according to my friends studying chemistry).
I don't know how hard economics is in VCE but honestly you'll have people saying that about every subject. If you're averaging 90+ in both I don't really think you should give them much thought.