Was doing a little research the other day on a related topic.
I came across a report on
Australasian Legal Information Institute (AustLII) that described an appeal against the suspension of an AOC. The operator had conducted an IFR charter from MER to CB in a C172
The interesting part was the detail that the beak went into when examining the issue of payment received.
He specifically mentioned and dismissed the old trick of "buy an orange from us and we will throw in a scenic flight for free" as a paper-thin fascade and noted "...I do not believe that it was the intention of the Federal Legislature to allow the CARs to be circumvented by such a scheme."
As others have said, you will probably get away with beraking the rules until something goes wrong. Chances are that CASA will be the least of your worries... I would be more worried about the insurer's QCs.