Virgin Australia fare structure

I am looking to book a flight from Brisbane to Mackay for my wife to travel up on Monday returning next Saturday and upon checking Virgin, I noticed the flight from Brisbane to Mackay was cheaper when loaded as a one way only $365, compared to the same leg being $394 when loaded as a return journey. Is this a fault with the virgin booking system or normal practice?

I have noticed at times QF is the same, they seem to sometimes load the return leg at a higher rate than the outgoing leg, first noticed it when I went to book to bring family up from BNE and was going to return back to BNE with them as I had business down there, my outgoing leg was cheaper than their return leg on the same flight, my return leg was also more expensive, so I booked two one way fares in each direction.

The Virgin booking system does that some times. You may find that the overall price of booking two one ways is the same as booking a return, as the return flight from Mackay may have a price difference the other way to make up the difference.

Compare booking as two one ways, versus booking a return.

You'll find the return is the same or -$1 than the one way fares combined. An outdated system imo.