Generally, 1 commerce or law subject will be about $1200 if you add it to HECS.
Some maths subjects will be less, but because fees are done in tiers for national priority and all that junk, pretty much it will be $1200 a subject.
So, for your Comm/Law course that is a minimum of 40 subjects, meaning about $48000 plus interest (if you do HECs)
It isn't unreasonable; Obviously your considering doing a double degree because you want to have the most options and skills to get you ahead in life. When you consider even just grad salaries in accounting for instance, most sit around 50k. So, if your willing to sacrifice your salary sooner, you can repay it sooner. Or, you just have the minimum taken with your tax every year and not worry about it. A lady from my work who recently turned 30 is only now paying off her HECs because she didn't care. Hasn't stopped her from doing anything in life!
I personally would suggest, despite the cost being higher, to do the combined degree. You're giving yourself more options in life. Commerce and Law are fairly popular degree choices and so there is a lot of people to compete with for jobs. Doing the combined degree gives yourself just a few more options.
