As others have said this is a standard change fee, not really a contact service fee, to discourage people buying cheaper sale tickets and then trying to make a change. I do not see why this would cause QF to lose money when in fact it may be increasing their revenue by requiring pax wishing flexibility to pay a higher fare.
If you really want to upgrade you can do it at the airport @$450 pp ow but not get luggage or Business Class QFF points or status credits.
I do not know your reasons why you wanted to book the way you did, the Business Class Saver fare was clear to see on the the same booking page, I usually do the calculations in my head to see how much extra it is.