Don't think 'Scaling' really matters.
People get over-worried about which subjects scale more and which subjects scale less...
All you have to do is get Band 5 or higher in all your subjects, and your pretty much on your way to 75+ Atar (depending on School rank; your rank and how your hsc...
Studying for Economics isn't hard. There is alot of content in the course but if you know how to link all the major topics & draw out implications, you'll be well on your way to a Band 6.
As for Physics, you just gotta sit down and learn/memorise the dot-points/concepts which you find the most...