not as cheap as this previous deal but reasonable for euro return tickets.
cheaper flights appear in Febraury to June
Site suggests cheapest available tickets are:
From Brisbane to Amsterdam from 1,336* AUD
From Adelaide to Amsterdam from 1,482* AUD
From Sydney to Amsterdam from 1,331* AUD
From Melbourne to Amsterdam from 1,316* AUD
From Perth to Amsterdam from 1,211* AUD
checked the dates of depart 6/4/16 - return 22/4/16 and got the following
perth <> amsterdam 6/4/16 - 22/4/16 $1,238.70
melbourne <> amsterdam 6/4/16 - 22/4/16 $1,344
sydney <> amsterdam 6/4/16 - 22/4/16 $1,358.38
Brisbane $1641
but Bris 10/4/16 - 22/4/16 1,466.36
have a play and see what you get.
some of these flights might be code sharing. so you might be with another airline rather than KLM.
KLM don't fly in/out of Australia so half the trip will be with another airline. Most of their codeshare partners are pretty reputable airlines though so not a big problem.