The Quarterly does give some insight into their opex. They 1st...

The Quarterly does give some insight into their opex.

They 1st produced on Nov 12th, shipping 10 tonnes on Jan 3rd. Assuming they had no initial stockpile, it took 52 days to produce 10 tonnes. The Quarterly shows the cost of production to be $3.25m, for this they received US$3m or A$4m. Ignoring overheads etc, a profit of $750k remembering half had been pre-payed, so really A$4.75m.

The Quarterly also says they expect to pay $11.2m this current Q for production.
The next ship is booked for Feb 17th, 45 days after the last shipment. If they do another 10 tonnes, means they've increased their production rate from 52 days down to 45, if its more than 10 tonnes - even better. You'd expect as they ramp up production for the time taken & cost to reduce.

Based on the $11.2m expected, they will produce at least 34,000 tonnes, probably much higher because of the improvements during ramp up.

Once they've delivered the 1st 45,000 tonnes half of which was pre-payed at $600/t, they'll be getting the full $900/tonne.