@Deepp your calculation is correct except for the next 12 months the operation cost should be between $400 to $450 (not $328 dmt) as stated in the qtrly and SH conference call due to higher mining cost (strip ratio factor resulted from mining in new precinct).
Still a very impressive margin if you apply the $428 per dmt operating cost.
I reckon the revised resource number for SDV to be announced in the next few weeks will rocket the SP further before or after the MERGER.