Ann: Sinclair Mine Complete, First Caesium Shipment Scheduled, page-6

That is a nice upside surprise, with the project being deemed economic on 1047 tonne of cesium yield, the additional 593 tonne has very little additional extraction cost to bear. On that basis most of the extra will go to profit.
Early media reports indicated $10m of net profit after the $4.8m Cabots loan repayment, so pricing the caesium around $15000/t. Giving a value to the additional caesium in the stock pile at around $6m.