The PFS had an after recovery ore value of $32.67 per tonne using the feasibility base case prices. The PFS had a cost of $12.46 per tonne to mine and process that ore. Therefore, the operating profit was $20.21 per tonne.

If you apply the lower grades from the BFS, the ore value drops to $29.50 per tonne. Then applying the lower recoveries further reduces the ore value to $27.74 per tonne. The operating cost of $13.33 per tonne leaves an operating profit of $14.41 per tonne.

The lower grade, lower recovery, and higher operating costs of the BFS largely account for why the economics of the PFS were not realised. I don't think this has anything to do with the inferred resource.