A$600 is outrageously high for a service fee for booking a LONE5 fare. My last DONE4 booking service fee (non-refundable, paid to the TA) was under $100, and that agent worked really hard for it!

Of course, we have a commercial agreement with our corporate travel agent, and as such the fee is fixed. The TA then passes the corporate discount that our company has negotiated with QF directly to us. So I would expect a TA may want a slightly higher service fee, but A$600 seems way over the top to me.