Just worth noting that (unlike in the US) Australian domestic airlines sell general fares on a one way basis. Things like complicated rules and Saturday night stays are very much a thing of the past down under.

It is often cost-effective to travel one direction with Virgin Blue and the other Jetstar, depending on which has the best pricing when you want to travel.

As for days of lower yields, you are spot on, except that on Saturdays it's not so much the day but evenings. (If you are travelling during peaks, like school holidays, expect prices to be substantially higher.)

Pricing on domestic airlines is extremely variable, often with multiple changes throughout a week. But anything under AUD50 is probably a good discount price for either direction on that route. Be patient, check back to the websites often and grab it when you see it!