UNSW requires a minimum WAM of 75 to transfer internally to Commerce double degrees under the Internal Program Transfer, as well as degree-specific criteria, such as a certain level of performance in specific subjects.
This information is available on the following page:
If you want to switch degrees, find a list of all undergraduate programs available by faculty for Internal Program Transfer at UNSW.
www.unsw.edu.au
With that being said, it seems that maximising your chances of successfully transferring to your desired degree(s) at UNSW specifically would entail not just meeting, but exceeding the minimum WAM requirement for the relevant degree(s), hence your friends' suggestion that you may need a WAM around 80 in this case to successfully transfer.
I hope this helps!
