"Unfortunately paying for seat selection at time of booking has become the norm for most airlines, not just Qantas."
The OP made no mention of any seat selection at time of booking, just simply stated a incident where a married couple booked two tickets ("booked as one") and ended up being assigned seats in different parts of the aircraft for the duration of a medium haul flight. One would think that if the booking was made as one, at the very least, the airline could ensure that they were seated beside each other.
That QF Customer Service would have been able to provide seating together at the cost of points or cash, show that the seating together was possible, and therefore attaching a cost to make it happen quite simply smacks of gouging.
QF tries to present as the champion and spirit of Australia, but reports like this just make one further believe that it is all a facade.